Organometallic complex, composition and light emitting element including the organometallic complex

ABSTRACT

To provide a novel organometallic complex, and light emitting elements, light emitting devices, and electronic devices which include the organometallic complex. In addition, to provide a composition in which the organometallic complex is dissolved and to provide a method for manufacturing light emitting elements using the composition. An organometallic complex has high solubility in a solvent. In the organometallic complex, the ligand including a pyrazine skeleton is bound to an atom belonging to Group 9 (Co, Rh, or Ir) or an atom belonging to Group 10 (Ni, Pd, or Pt). In addition, the light emission efficiency is high. Therefore, the organometallic complex is preferably used for manufacturing a light emitting element.

TECHNICAL FIELD

The present invention relates to organometallic complexes andcompositions including the organometallic complexes. Further, thepresent invention relates to light emitting elements, light emittingdevices, and electronic devices which use electroluminescence, and amethod for manufacturing the light emitting elements.

BACKGROUND ART

Organic compounds absorb light to be in an excited state. Organiccompounds cause various reactions (such as photochemical reactions) oremit light (luminescence) in some cases through this excited state.Therefore, various applications of the organic compounds have been beingmade.

As one example of the photochemical reactions, there is a reaction(oxygen addition) of singlet oxygen with an unsaturated organic molecule(for example, see Non-patent Document 1: Haruo INOUE, et al., BasicChemistry Course PHOTOCHEMISTRY I (published by Maruzen Co., Ltd.), pp.106-110). Since the ground state of an oxygen molecule is a tripletstate, oxygen in a singlet state (singlet oxygen) is not generated bydirect photoexcitation. Singlet oxygen is generated in the presence ofany other triplet excited molecule, which leads to an oxygen additionreaction. A compound which can be the triplet excited molecule isreferred to as a photosensitizer.

As described above, a photosensitizer that can make a triplet excitedmolecule by photoexcitation is necessary in order to generate singletoxygen. However, since the ground state of an ordinary organic compoundis a singlet state, photoexcitation to a triplet excited state is aforbidden transition and a triplet excited molecule is unlikely formed.Therefore, a compound that can easily cause intersystem crossing from asinglet excited state to a triplet excited state (or a compound thatallows a forbidden transition and is directly photoexcited to thetriplet excited state) is required as a photosensitizer. In other words,such a compound can be used as a photosensitizer and is useful.

The compound often exhibits phosphorescence. Phosphorescence refers toluminescence generated by transition between different energies inmultiplicity. In an ordinary organic compound, phosphorescence refers toluminescence generated in returning from the triplet excited state tothe singlet ground state (in contrast, fluorescence refers toluminescence in returning from the singlet excited state to the singletground state). Fields of application of a compound capable of exhibitingphosphorescence, that is, a compound capable of converting the tripletexcited state into luminescence (hereinafter, referred to as aphosphorescent compound), include a light emitting element including anorganic compound as a light emitting substance.

Such a light emitting element has a simple structure in which a lightemitting layer including an organic compound which is a light emittingsubstance is provided between electrodes. This light emitting elementattracts attention as a next-generation flat panel display elementbecause of its characteristics such as a thin shape, lightweight, highresponse speed, and direct current low voltage driving. Further, adisplay device including this light emitting element is superior incontrast, image quality, and has a wide viewing angle.

In a light emitting element including an organic compound as a lightemitting substance, an emission mechanism is a carrier injection type.In other words, when voltage is applied between electrodes whichsandwich a light emitting layer, electrons and holes are injected fromthe electrodes and recombined to make the light emitting substanceexcited, and then, light is emitted when the electrons and holes returnfrom the excited state to the ground state. As in the case ofphotoexcitation described above, types of the excited state include asinglet excited state (S*) and a triplet excited state (T*). Thestatistical generation ratio thereof in the light emitting element isconsidered to be S*:T*=1:3.

A compound capable of converting the singlet excited state toluminescence (hereinafter, referred to as a fluorescent compound)exhibits only luminescence from the singlet excited state(fluorescence), and does not exhibit luminescence from the tripletexcited state (phosphorescence) at room temperature. Accordingly, theinternal quantum efficiency (the ratio of generated photons to injectedcarriers) of a light emitting element including a fluorescent compoundis assumed to have a theoretical limit of 25% based on S*:T*=1:3.

On the other hand, if the above-described phosphorescent compound isused, the internal quantum efficiency can be improved up to 75 to 100%in theory; that is, the light emission efficiency can be 3 to 4 times ashigh as that of a fluorescent compound is possible. Therefore, lightemitting elements including a phosphorescent compound has been activelydeveloped in recent years in order to realize highly-efficient lightemitting elements (for example, see Non-patent Document 2: ChihayaADACHI, et al., Applied Physics Letters, Vol. 78, No. 11, pp. 1622-1624.(2001)). An organometallic complex that includes iridium or the like asa central metal is particularly attracting attention as a phosphorescentcompound because of its high phosphorescence quantum efficiency.

DISCLOSURE OF INVENTION

An organometallic complex like the organometallic complex disclosed inNon-patent Document 2 is expected to be used as a photosensitizerbecause it causes intersystem crossing easily. Further, since theorganometallic complex exhibits luminescence (phosphorescence) from atriplet excited state easily, application of the organometallic complexto a light emitting element raises expectations for a highly-efficientlight emitting element. However, in the present state, the number ofkinds of such organometallic complexes is small.

Furthermore, a film of an organometallic complex such as theorganometallic complex disclosed in Non-patent Document 2 is typicallyformed by a vacuum evaporation method and used for a light emittingelement. However, a vacuum evaporation method has problems such as lowmaterial use efficiency and limitation on substrate size. Therefore, afilm forming method other than a vacuum evaporation method has beenexamined for productization and mass production of light emittingelements.

A droplet discharge method or a spin coating method has been proposed asa method for forming an organic compound film over a large substrate. Insuch film formation, a solution in which an organic compound isdissolved in a solvent is used.

However, the above-described organometallic complex has low solubility,and accordingly, it has been impossible to prepare a solution with asufficiently high concentration which can be used for film formation bya droplet discharge method or a spin coating method.

Thus, it is an object of the present invention to provide a novelorganometallic complex.

It is another object of the present invention to provide a compositionin which the organometallic complex is dissolved and to provide a methodfor manufacturing light emitting elements using the composition.

Furthermore, another object of the present invention is to provide alight emitting element, a light emitting device, and an electronicdevice which are manufactured using the organometallic complex.

The inventors of the present invention have found that an organometalliccomplex represented by a general formula (G1) has high solubility in asolvent.

An aspect of the present invention is an organometallic complexrepresented by the general formula (G1).

In the formula, Ar represents an arylene group; R¹ represents an alkylgroup or an aryl group; R² represents any one of hydrogen, an alkylgroup, or an aryl group; and R³ represents hydrogen or an alkyl group.Note that R² and R³ may be bound to each other to form an alicyclicring. In addition, M is a central metal and represents either an elementbelonging to Group 9 or an element belonging to Group 10. In addition, nis 2 when M is an element belonging to Group 9, and n is 1 when M is anelement belonging to Group 10. One of R²¹ and R²² represents an alkylgroup having 2 to 10 carbon atoms or a haloalkyl group having 2 to 10carbon atoms and the other one represents an alkyl group having 1 to 10carbon atoms or a haloalkyl group having 1 to 10 carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G1).

In the formula, Ar represents an arylene group; R¹ represents an alkylgroup or an aryl group; R² represents any one of hydrogen, an alkylgroup, or an aryl group; and R³ represents hydrogen or an alkyl group.Note that R² and R³ may be bound to each other to form an alicyclicring. In addition, M is a central metal and represents either an elementbelonging to Group 9 or an element belonging to Group 10. In addition, nis 2 when M is an element belonging to Group 9, and n is 1 when M is anelement belonging to Group 10. One of R²¹ and R²² represents an alkylgroup having 2 to 4 carbon atoms or a haloalkyl group having 2 to 4carbon atoms and the other one represents an alkyl group having 1 to 4carbon atoms or a haloalkyl group having 1 to 4 carbon atoms.

An aspect of the present invention is an organometallic complexrepresented by the general formula (G1).

In the formula, Ar represents an arylene group; R¹ represents an alkylgroup or an aryl group; R² represents any one of hydrogen, an alkylgroup, and an aryl group; and R³ represents hydrogen or an alkyl group.Note that R² and R³ may be bound to each other to form an alicyclicring. In addition, M is a central metal and represents either an elementbelonging to Group 9 or an element belonging to Group 10. In addition, nis 2 when M is an element belonging to Group 9, and n is 1 when M is anelement belonging to Group 10. One of R²¹ and R²² represents a branchedalkyl group having 3 to 4 carbon atoms and the other one represents analkyl group having 1 to 4 carbon atoms or a haloalkyl group having 1 to4 carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G1).

In the formula, Ar represents an arylene group; R¹ represents an alkylgroup or an aryl group; R² represents any one of hydrogen, an alkylgroup, or an aryl group; R3 represents hydrogen or an alkyl group. Notethat R² and R³ may be bound to each other to form an alicyclic ring. Inaddition, M is a central metal and represents either an elementbelonging to Group 9 or an element belonging to Group 10. In addition, nis 2 when M is an element belonging to Group 9, and n is 1 when M is anelement belonging to Group 10. Each of R²¹ and R²² represents a branchedalkyl group having 3 to 4 carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by a general formula (G2).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R² represents any one ofhydrogen, an alkyl group, a phenyl group, or a phenyl group having asubstituent; and R³ represents hydrogen or an alkyl group. Note that R²and R³ may be bound to each other to form an alicyclic ring. Inaddition, each of R⁴ to R⁷ represents any one of hydrogen, an alkylgroup, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. One of R²¹ and R²²represents an alkyl group having 2 to 10 carbon atoms or a haloalkylgroup having 2 to 10 carbon atoms and the other one represents an alkylgroup having 1 to 10 carbon atoms or a haloalkyl group having 1 to 10carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G2).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R² represents any one ofhydrogen, an alkyl group, a phenyl group, or a phenyl group having asubstituent; and R³ represents hydrogen or an alkyl group. Note that R²and R³ may be bound to each other to form an alicyclic ring. Inaddition, each of R⁴ to R⁷ represents any one of hydrogen, an alkylgroup, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. M is a central metal and represents either anelement belonging to Group 9 or an element belonging to Group 10. Inaddition, n is 2 when M is an element belonging to Group 9, and n is 1when M is an element belonging to Group 10. One of R²¹ and R²²represents an alkyl group having 2 to 4 carbon atoms or a haloalkylgroup having 2 to 4 carbon atoms and the other one represents an alkylgroup having 1 to 4 carbon atoms or a haloalkyl group having 1 to 4carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G2).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R² represents any one ofhydrogen, an alkyl group, a phenyl group, or a phenyl group having asubstituent; and R³ represents hydrogen or an alkyl group. Note that R²and R³ may be bound to each other to form an alicyclic ring. Inaddition, each of R⁴ to R⁷ represents any one of hydrogen, an alkylgroup, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. M is a central metal and represents either anelement belonging to Group 9 or an element belonging to Group 10. Inaddition, n is 2 when M is an element belonging to Group 9, and n is 1when M is an element belonging to Group 10. One of R²¹ and R²²represents a branched alkyl group having from 3 to 4 carbon atoms andthe other one represents an alkyl group having 1 to 4 carbon atoms or ahaloalkyl group having 1 to 4 carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G2).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R² represents any one ofhydrogen, an alkyl group, a phenyl group, or a phenyl group having asubstituent; and R³ represents hydrogen or an alkyl group. Note that R²and R³ may be bound to each other to form an alicyclic ring. Inaddition, each of R⁴ to R⁷ represents any one of hydrogen, an alkylgroup, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. Each of R²¹ and R²²represents a branched alkyl group having 3 to 4 carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by a general formula (G3).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R³ represents hydrogen or analkyl group; and each of R⁴ to R¹² represents any one of hydrogen, analkyl group, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. One of R²¹ and R²²represents an alkyl group having 2 to 10 carbon atoms or a haloalkylgroup having 2 to 10 carbon atoms and the other one represents an alkylgroup having 1 to 10 carbon atoms or a haloalkyl group having 1 to 10carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G3).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R³ represents hydrogen or analkyl group; and each of R⁴ to R¹² represents any one of hydrogen, analkyl group, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. One of R²¹ and R²²represents an alkyl group having 2 to 4 carbon atoms or a haloalkylgroup having 2 to 4 carbon atoms and the other one represents an alkylgroup having 1 to 4 carbon atoms or a haloalkyl group having 1 to 4carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G3).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R³ represents hydrogen or analkyl group; and each of R⁴ to R¹² represents any one of hydrogen, analkyl group, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. One of R²¹ and R²²represents a branched alkyl group having 3 to 4 carbon atoms and theother one represents an alkyl group having 1 to 4 carbon atoms or ahaloalkyl group having 1 to 4 carbon atoms.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G3).

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R³ represents hydrogen or analkyl group; and each of R⁴ to R¹² represents any one of hydrogen, analkyl group, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. Each of R²¹ and R²²represents a branched alkyl group having 3 to 4 carbon atoms.

In the above-described structures, the central metal M is preferablyiridium or platinum in terms of emission efficiency.

Another aspect of the present invention is a composition including theabove-described organometallic complex and a solvent.

Note that any of the above-described organometallic complexes ispreferably dissolved in a solvent at a concentration of equal to orhigher than 0.6 g/L, in consideration of using the above-describedcomposition for manufacturing light emitting elements. More preferably,any of the above-described organometallic complexes is preferablydissolved in a solvent at a concentration of equal to or higher than 0.9g/L.

In the above-described composition, any of a variety of solvents can beused as the solvent. The above-described organometallic complexes aresoluble even in an organic solvent not including an aromatic ring.Further, the organometallic complexes are soluble even in ether oralcohol.

In consideration of using the above-described composition formanufacturing light emitting elements, it is preferable that the solventbe an organic solvent having a boiling point of equal to or higher than50° C. and equal to or less than 200° C. because the solvent needs to beremoved for film formation.

In the above-described composition, an organic semiconductor materialmay further be included.

Further, in the above-described composition, a binder may further beincluded.

The present invention includes a light emitting element manufacturedusing the above-described organometallic complex. In other word, anotheraspect of the present invention is a light emitting element includingthe above-described organometallic complex between a pair of electrodes.

The above-described organometallic complex has high light emissionefficiency, and therefore, is preferably used for a light emittinglayer. Accordingly, another aspect of the present invention is a lightemitting element including a light emitting layer between a pair ofelectrodes, in which the light emitting layer includes theabove-described organometallic complex.

Another aspect of the present invention is a light emitting elementincluding a layer including the above-described organometallic complexand a high molecular compound between a pair of electrodes. In theabove-described structure, the high molecular compound is an organicsemiconductor material.

In the above-described structure, the high molecular compound is abinder. In addition, the layer including an organometallic complex and ahigh molecular compound further includes an organic semiconductormaterial.

In the above-described structure, the layer including an organometalliccomplex and a high molecular compound is preferably a light emittinglayer.

In addition, a hole-transporting layer which is in contact with thelight emitting layer includes a low molecular compound. Further, anelectron-transporting layer which is in contact with the light emittinglayer includes a low molecular compound.

A light emitting device of the present invention includes theabove-described light emitting element. Further, a light emitting deviceof the present invention includes a control circuit which controls lightemission of the light emitting element. Note that a light emittingdevice in this specification refers to an image display device, a lightemitting unit, or a light source (including a lighting device). Further,the light emitting device also refers to a module in which a connectorsuch as a flexible printed circuit (FPC), a tape automated bonding (TAB)tape, or a tape carrier package (TCP) is attached to a panel or a modulein which a printed wiring board is provided at an end of a TAB tape or aTCP. Further, the light emitting device in this specification alsorefers to a light emitting element on which an integrated circuit (IC)is directly mounted by a chip on glass (COG) method.

The present invention also includes an electronic device which includesa light emitting element of the present invention in its displayportion. Accordingly, an electronic device of the present inventionincludes a display portion, in which the display portion includes theabove-described light emitting element and control circuit whichcontrols light emission of the light emitting element.

The present invention also includes a method for manufacturing a lightemitting element using the above-described composition. Thus, anotheraspect of the present invention is a method for manufacturing a lightemitting element, including forming a first electrode, applying theabove-described composition and removing a solvent, and forming a secondelectrode.

Another aspect of the present invention is a method for manufacturing alight emitting element, including forming a first electrode, forming alayer including an organic compound by an evaporation method, applyingthe above-described composition including a solvent and removing thesolvent, and forming a second electrode.

Another aspect of the present invention is a method for manufacturing alight emitting element, including forming a first electrode, applyingthe above-described composition including a solvent and removing thesolvent, forming a layer including an organic compound by an evaporationmethod, and forming a second electrode.

An organometallic complex of the present invention has a high solubilityin a solvent. In addition, an organometallic complex of the presentinvention has high light emission efficiency.

Further, a composition of the present invention has an organometalliccomplex dissolved therein and is preferably used for manufacturing lightemitting elements.

A method for manufacturing a light emitting element, which is suitablefor industrial application, can be realized using a composition of thepresent invention for manufacturing light emitting elements.

Light emitting elements manufactured using a composition of the presentinvention can have high emission efficiency.

A light emitting device and an electronic device of the presentinvention includes a light emitting element having high emissionefficiency, and therefore consumes less power.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a light emitting element of the present invention;

FIG. 2 illustrates a diagram illustrating a light emitting element ofthe present invention;

FIG. 3 illustrates a diagram illustrating a light emitting element ofthe present invention;

FIGS. 4A and 4B illustrate a light emitting element of the presentinvention;

FIGS. 5A and 5B illustrate a light emitting element of the presentinvention;

FIGS. 6A to 6D illustrate electronic devices of the present invention;

FIG. 7 illustrates an electronic device of the present invention;

FIG. 8 illustrates a lighting device of the present invention;

FIG. 9 illustrates a lighting device of the present invention;

FIGS. 10A to 10D illustrate a method for manufacturing a light emittingelement of the present invention;

FIG. 11 illustrates a method for manufacturing a light emitting elementof the present invention;

FIG. 12 illustrates the ¹H NMR spectrum ofbis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbr.:[Ir(tppr)₂(dpm)]);

FIG. 13 illustrates the absorption spectrum and the emission spectrum ofbis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbr.:[Ir(tppr)₂(dpm)]);

FIG. 14 illustrates the emission spectrum of a light emitting elementfabricated in Example 3;

FIG. 15 illustrates the ¹H NMR spectrum ofbis(2,3,5-triphenylpyrazinato)(pivaloyltrifluoroacetonato)iridium(III)(abbr.: [Ir(tppr)₂(pFac)]); and

FIG. 16 illustrates the absorption spectrum and the emission spectrum ofbis(2,3,5-triphenylpyrazinato)(pivaloyltrifluoroacetonato)iridium(II)(abbr.: [Ir(tppr)₂(pFac)]).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiment modes and examples of the present invention willbe described with reference to the drawings. Note that modes and detailsof the present invention can be modified in various ways withoutdeparting from the spirit and scope of the present invention.Accordingly, the present invention should not be construed as beinglimited to the description of the embodiment modes and the examplesgiven below.

Embodiment Mode 1

This embodiment mode describes an organometallic complex of the presentinvention and a composition including the organometallic complex.

An organometallic complex of the present invention has a ligandincluding a pyrazine skeleton which is cyclometalated to a centralmetal. There are various ligands including a pyrazine skeleton, and ifthe ligand is a 2-arylpyrazine derivative, the ligand can becyclometalated to a central metal. The cyclometalated complex has highphosphorescence quantum efficiency. Therefore, the ligand including apyrazine skeleton preferably is a 2-arylpyrazine derivative.

In addition, in an organometallic complex of the present invention, achelate ligand having a β diketone structure represented by a generalformula (L0) is coordinated to the central metal as well as theabove-described ligand including a pyrazine skeleton. In other words, anorganometallic complex of the present invention includes two kinds ofligands: a ligand including a pyrazine skeleton and a chelate ligandrepresented by the general formula (L0).

In the general formula (L0), one of R²¹ and R²² represents an alkylgroup having 2 to 10 carbon atoms or a haloalkyl group having 2 to 10carbon atoms and the other one represents an alkyl group having 1 to 10carbon atoms or a haloalkyl group having 1 to 10 carbon atoms.

The inventors of the present invention have found that an organometalliccomplex including above-described two kinds of ligands has extremelyhigh solubility in an organic solvent. In specific, the inventors of thepresent invention have found that an organometallic complex includingabove-described two kinds of ligands is soluble in a general alcoholsolvent such as methanol, ethanol, or isopropanol as well as in ahalogen-based solvent such as dichloromethane, dichloroethane, orchloroform; and an aromatic hydrocarbon-based solvent such as toluene orxylene.

Another aspect of the present invention is an organometallic complexrepresented by the general formula (G1).

In the formula, Ar represents an arylene group; R¹ represents an alkylgroup or an aryl group; R² represents any one of hydrogen, an alkylgroup, or an aryl group; and R³ represents hydrogen or an alkyl group.Note that R² and R³ may be bound to each other to form an alicyclicring. In addition, M is a central metal and represents either an elementbelonging to Group 9 or an element belonging to Group 10. In addition, nis 2 when M is an element belonging to Group 9, and n is 1 when M is anelement belonging to Group 10. One of R²¹ and R²² represents an alkylgroup having 2 to 10 carbon atoms or a haloalkyl group having 2 to 10carbon atoms and the other one represents an alkyl group having 1 to 10carbon atoms or a haloalkyl group having 1 to 10 carbon atoms.

In the organometallic complex represented by the general formula (G1),the ligand including a pyrazine skeleton is bound to an atom belongingto Group 9 (Co, Rh, or Ir) or an atom belonging to Group 10 (Ni, Pd, orPt). That is, the central metal is an element belonging to Group 9 or anelement belonging to Group 10. The binding of the ligand including apyrazine skeleton to an element belonging to Group 9 or an elementbelonging to Group 10 can achieve high light emission efficiency.

Since an organometallic complex represented by the general formula (G1)has extremely high solubility in a solvent, the concentration of theorganometallic complex in a solution can be adjusted as appropriate forforming a layer including the organometallic complex. In addition, anorganometallic complex represented by the general formula (G1) issoluble in a general alcohol solvent such as methanol, ethanol, orisopropanol as well as in a halogen-based solvent such asdichloromethane, dichloroethane, or chloroform or an aromatichydrocarbon-based solvent such as toluene or xylene; therefore, thereare many choices for solvents. Accordingly, it is possible to form alayer including an organometallic complex represented by the generalformula (G1) by a wet process over a layer that has been already formed.

Further, when a 2-phenylpyrazine derivative which is a kind of a2-arylpyrazine derivative is the ligand, the ligand can be subjected toorthometallation with the central metal (orthometallation is a kind ofcyclometalation). An orthometallated complex including thusorthometallated 2-phenylpyrazine can have particularly highphosphorescence quantum efficiency. Therefore, a preferred mode of theligand including a pyrazine skeleton is a 2-phenylpyrazine derivative.An organometallic complex represented by the general formula (G2) isgiven as an organometallic complex including an orthometallated2-phenylpyrazine derivative.

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R² represents any one ofhydrogen, an alkyl group, a phenyl group, or a phenyl group having asubstituent; and R³ represents hydrogen or an alkyl group. Note that R²and R³ may be bound to each other to form an alicyclic ring. Inaddition, each of R⁴ to R⁷ represents any one of hydrogen, an alkylgroup, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. One of R²¹ and R²²represents an alkyl group having 2 to 10 carbon atoms or a haloalkylgroup having 2 to 10 carbon atoms and the other one represents an alkylgroup having 1 to 10 carbon atoms or a haloalkyl group having 1 to 10carbon atoms.

In the general formula (G2), if R² is a substituted or unsubstitutedphenyl group, red-color light emission with high color purity and highluminous efficiency (cd/A) can be obtained. In other words, amongorganometallic complexes in which a 2-phenylpyrazine derivative isorthometallated, an organometallic complex in which a2,5-diphenylpyrazine derivative is orthometallated is preferable. Anorganometallic complex represented by the general formula (G3) is givenas an organometallic complex including an orthometallated2,5-diphenylpyrazine derivative.

In the formula, R¹ represents any one of an alkyl group, a phenyl group,or a phenyl group having a substituent; R³ represents hydrogen or analkyl group; and each of R⁴ to R¹² represents any one of hydrogen, analkyl group, a halogen group, a haloalkyl group, an alkoxy group, or analkoxycarbonyl group. In addition, M is a central metal and representseither an element belonging to Group 9 or an element belonging to Group10. In addition, n is 2 when M is an element belonging to Group 9, and nis 1 when M is an element belonging to Group 10. One of R²¹ and R²²represents an alkyl group having 2 to 10 carbon atoms or a haloalkylgroup having 2 to 10 carbon atoms and the other one represents an alkylgroup having 1 to 10 carbon atoms or a haloalkyl group having 1 to 10carbon atoms.

In the above-described structure, an arylene group having 6 to 25 carbonatoms is preferably used as an arylene group Ar. In specific, asubstituted or unsubstituted 1,2-phenylene group, 8,9-julolidylenegroup, 1,2-naphthylene group, 2,3-naphthylene group, spirofluorene-2,3-diyl group, or 9,9-dialkylfluorene-2,3-diyl group such as a9,9-dimethylfluorene-2,3-diyl group can be employed. If the arylenegroup Ar is a substituted or unsubstituted 1,2-phenylene group, rise invaporizing temperature caused by increase in molecular weight can besuppressed, which is especially advantageous when the organometalliccomplex is vaporized for sublimation purification or the like. In thecase where the 1,2-phenylene group has a substituent, specific examplesof the substituent are an alkyl group such as a methyl group, an ethylgroup, an isopropyl group, or a tert-butyl group; an alkoxy group suchas a methoxy group, an ethoxy group, an isopropoxy group, or atert-butoxy group; an aryl group such as a phenyl group or a4-biphenylyl group; a halogen group such as a fluoro group; a haloalkylgroup such as a trifluoromethyl group; and an alkoxycarbonyl group suchas a methoxycarbonyl group, an ethoxycarbonyl group, an isopropoxycarbonyl group, or a tert-butoxycarbonyl group. Note that anunsubstituted 1,2-phenylene group is particularly preferable among thespecific examples of the arylene group Ar.

In the above-described structure, the aryl group can be a substituted orunsubstituted phenyl group, 1-naphthyl group, 2-naphthyl group,spirofluorene-2-yl group, 9,9-dialkylfluorene-2-yl group such as a9,9-dimethylfluorene-2-yl group, or the like. Note that an aryl grouphaving 6 to 25 carbon atoms is preferable in consideration of solubilityin a solvent. In the case of the above-described aryl group has asubstituent, the substituent can be an alkyl group such as a methylgroup, an ethyl group, an isopropyl group, or a tert-butyl group; analkoxy group such as a methoxy group, an ethoxy group, an isopropoxygroup, or a tert-butoxy group; an aryl group such as a phenyl group or a4-biphenylyl group; a halogen group such as a fluoro group; a haloalkylgroup such as a trifluoromethyl group; or an alkoxycarbonyl group suchas a methoxycarbonyl group, an ethoxycarbonyl group, an isopropoxycarbonyl group, or a tert-butoxycarbonyl group.

Further in the above-described structure, the substituent of the phenylgroup having a substituent can be an alkyl group such as a methyl group,an ethyl group, an isopropyl group, or a tert-butyl group; an alkoxygroup such as a methoxy group, an ethoxy group, an isopropoxy group, ora tert-butoxy group; an aryl group such as a phenyl group or a4-biphenylyl group; a halogen group such as a fluoro group; a haloalkylgroup such as a trifluoromethyl group; and an alkoxycarbonyl group suchas a methoxycarbonyl group, an ethoxycarbonyl group, an isopropoxycarbonyl group, or a tert-butoxycarbonyl group can be given.

In the above-described structure, the alkyl group can be a methyl group,an ethyl group, an isopropyl group, a tert-butyl group, a cyclohexylgroup, a pentyl group, or the like. Note that an alkyl group having 5 ormore carbon atoms is preferable in consideration of solubility of theabove-described organometallic complex in a solvent. However, theabove-described organometallic complex has high solubility even in thecase of having an alkyl group having 4 or less carbon atoms. In otherwords, it is one aspect of an organometallic complex of the presentinvention that the alkyl group is an alkyl group having 4 or less carbonatoms, such as a methyl group, an ethyl group, an isopropyl group, or atert-butyl group, in the above-described organometallic complex.

In the above-described structure, a fluoro group, a chloro group, or thelike can be given as a halogen group, and a fluoro group is preferablein terms of chemical stability. As a haloalkyl group, a trifluoromethylgroup is preferable.

In the above-described structure, the alkoxy group can be a methoxygroup, an ethoxy group, an isopropoxy group, a tert-butoxy group, or thelike. The above-described organometallic complex has high solubilityeven in the case of having an alkoxy group having 4 or less carbonatoms. In other words, it is one aspect of an organometallic complex ofthe present invention that the alkoxy group is an alkoxy group having 4or less carbon atoms, such as a methoxy group, an ethoxy group, anisopropoxy group, or a tert-butoxy group, in the above-describedorganometallic complex.

In the above-described structure, an alkoxycarbonyl group can be amethoxycarbonyl group, an ethoxycarbonyl group, an isopropoxy carbonylgroup, a tert-butoxycarbonyl group, or the like. The above-describedorganometallic complex has high solubility even in the case of having analkoxycarbonyl group having 5 or less carbon atoms. In other words, itis one aspect of an organometallic complex of the present invention thatthe alkoxycarbonyl group is an alkoxycarbonyl group having 5 or lesscarbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group,an isopropoxy carbonyl group, or a tert-butoxycarbonyl group.

In the above-described general formula (L0) and the general formulae(G1) to (G3), one of R²¹ and R²² represents an alkyl group having 2 to10 carbon atoms or a haloalkyl group having 2 to 10 carbon atoms and theother one represents an alkyl group having 1 to 10 carbon atoms or ahaloalkyl group having 1 to 10 carbon atoms. The inventors of thepresent invention have found that an organometallic complex of thepresent invention can have sufficient solubility when any one of ligandsrepresented by general formulae (L1) to (L10) can be given as a ligandrepresented by the general formula (L0), in other words, either R²¹ orR²² has 2 or more carbon atoms.

As the number of carbon atoms in R²¹ and R²² is increased, thesolubility is improved. However, the solubility of the above-describedorganometallic complex is high even when each of R²¹ and R²² are analkyl group having 4 or less carbon atoms or a haloalkyl group having 4or less carbon atoms. In other words, it is one aspect of anorganometallic complex of the present invention that each of R²¹ and R²²are an alkyl group having 4 or less carbon atoms such as a methyl group,an ethyl group, an isopropyl group, or a tert-butyl group or a haloalkylgroup having 4 or less carbon atoms such as a trifluoromethyl group.

Therefore, in the above-described general formula (L0) and the generalformulae (G1) to (G3), it is preferable that one of R²¹ and R²²represent an alkyl group having 2 to 4 carbon atoms or a haloalkyl grouphaving 2 to 10 carbon atoms and the other one represent an alkyl grouphaving 1 to 4 carbon atoms or a haloalkyl group having 1 to 4 carbonatoms.

An organometallic complex of the present invention has high solubilityeven without a long chain alkyl group; therefore, movement of carriersis not interrupted when the organometallic complex of the presentinvention is used for a light emitting element. In addition, when anorganometallic complex of the present invention is used as a lightemitting substance of the light emitting element, there is an advantagethat carrier injection to the organometallic complex of the presentinvention is not interrupted.

Further, it is particularly preferable that each of R²¹ and R²² be abranched alkyl group, because the solubility is further improved.

Therefore, in the above-described general formula (L0) and the generalformulae (G1) to (G3), it is preferable that one of R²¹ and R²²represent a branched alkyl group having 3 to 4 carbon atoms and theother one represent an alkyl group having 1 to 4 carbon atoms or ahaloalkyl group having 1 to 4 carbon atoms.

Further, it is preferable that each of R²¹ and R²² be a branched alkylgroup, because the solubility is further improved.

Therefore, in the foregoing general formula (L0) and the generalformulae (G1) to (G3), each of R²¹ and R²² preferably represents abranched alkyl group having 3 to 4 carbon atoms.

In addition, in the general formulae (G1) to (G3), R³ is preferablyhydrogen for convenience of synthesis. It is preferable that R³ behydrogen in terms of synthetic yield because steric hindrance of aligand is reduced and the ligand is easily bonded to a metal ion.

Further in addition, iridium and platinum are preferable as the centralmetal M of the above-described organometallic complex in terms of heavyatom effect. In particular, iridium is preferable because iridium ischemically stable and shows pronounced heavy atom effect which leads tohigh efficiency.

Organometallic complexes represented by structural formulae (101) to(178) are given as specific examples of the above-describedorganometallic complex, but the present invention is not limited tothose organometallic complexes.

Various reactions can be applied to a synthetic method for anorganometallic complex of the present invention. For example, aderivative of an organometallic complex of the present invention can besynthesized by a synthesis reaction described below. Note that asynthetic method for forming an organometallic complex of the presentinvention is not limited to the synthetic methods below.

<<A Synthetic Method for a Pyrazine Derivative Represented by theGeneral Formula (G0)>>

An organometallic complex of the present invention is formed throughorthometallation of a pyrazine derivative represented by the generalformula (G0) with an ion of a metal element belonging to Group 9 orGroup 10.

A pyrazine derivative represented by the general formula (G0) can besynthesized by a simple synthetic scheme such as the one given below.For example, as shown in a following scheme (a), a halide of arene (A1)is lithiated with alkyl lithium or the like, and is reacted withpyrazine (A2), whereby a pyrazine derivative represented by the generalformula (G0) is obtained. Alternatively, as shown in a following scheme(a1), a pyrazine derivative represented by the general formula (G0) canbe obtained by coupling a boronic acid of arene (A1-1) and a halide ofpyrazine (A2-1). Further alternatively, as shown in a following scheme(a2), a pyrazine derivative represented by the general formula (G0) canbe obtained by reaction of diketone of arene (A1-2) and diamine (A2-2).Further alternatively, as shown in a following scheme (a3), a pyrazinederivative represented by the general formula (G0) can be obtained byreaction of pyrazine of arene (A1-3) and a lithio derivative or aGrignard reagent (A2-3). Note that X in those synthetic schemesrepresents a halogen element.

Since various kinds of the above-described compounds (A1), (A2), (A1-1),(A2-1), (A2-2), (A1-3), and (A2-3) are available commercially or can besynthesized, many kinds of a pyrazine derivative represented by thegeneral formula (G0) can be synthesized. Accordingly, an organometalliccomplex of the present invention has wide variations of ligands.

<<A Synthetic Method for an Organometallic Complex of the PresentInvention which is Represented by the General Formula (G1)>>

Next, an organometallic complex of the present invention which is formedthrough orthometallation of a pyrazine derivative represented by thegeneral formula (G0), i.e., an organometallic complex represented by thefollowing general formula (G1) is described.

First, as shown in a following synthesis scheme (b), a pyrazinederivative represented by the general formula (G0) and a compound of ametal belonging to Group 9 or Group 10 which includes a halogen (such asa metal halide or a metal complex) are heated in an appropriate solventto obtain a binuclear complex (B). As the solvent, water, alcohols(glycerol, ethylene glycol, 2-ethoxyethanol, 2-methoxyethanol, or thelike), ethers (dioxane, anisole, or the like), or the like can be usedalone or two or more kinds of them can be mixed and used. A compound ofa metal belonging to Group 9 or Group 10 which includes a halogen canbe, but not exclusively, rhodium chloride hydrate, palladium chloride,iridium chloride hydrate, iridium chloride hydrate hydrochloride,potassium tetrachloroplatinate(II), or the like. Note that in thesynthesis scheme (b), M represents an element belonging to Group 9 orGroup 10 and X represents a halogen element. In addition, n is 2 when Mis an element belonging to Group 9, and n is 1 when M is an elementbelonging to Group 10.

Then, as shown in a following synthesis scheme (c), the binuclearcomplex (B) and a ligand represented by the general formula (L0) havinga βdiketone structure are heated in an appropriate solvent in thepresence of a base to obtain an organometallic complex of the presentinvention which is represented by the general formula (G1). As thesolvent, water, alcohols (glycerol, ethylene glycol, 2-ethoxyethanol,2-methoxyethanol, or the like), ethers (dioxane, anisole, or the like),or the like can be used alone or two or more kinds of them can be mixedand used. Note that in the synthesis scheme (c), M represents an elementbelonging to Group 9 or Group 10 and X represents a halogen element. Inaddition, n is 2 when M is an element belonging to Group 9, and n is 1when M is an element belonging to Group 10.

A composition including an organometallic complex of the presentinvention is also included in the scope of the present invention.Therefore, a composition of the present invention refers to acomposition including the above-described organometallic complex and asolvent.

Various kinds of solvents can be used in the above-describedcomposition. For example, the above-described organometallic complex issoluble in a solvent having an aromatic ring (e.g., a benzene ring),such as toluene, xylene, or methoxybenzene (anisole). Further, theabove-described organometallic complex is soluble in an organic solventnot including an aromatic ring, such as dimethylsulfoxide (DMSO),dimethylformamide (DMF), or chloroform.

In addition, the above-described organometallic complex is soluble inether such as diethyl ether or dioxane; or alcohol such as methanol,ethanol, isopropanol, butanol, 2-methoxyethanol, or 2-ethoxyethanol. Acomposition including alcohol as a solvent has a great advantage whenbeing used for manufacturing a light emitting element, in that EL layersof a light emitting element can be stacked. In other words, a layer canbe formed using a composition which includes alcohol as a solvent over alayer including an organic compound which is formed by an evaporationmethod or the like.

Note that in consideration of using the above-described composition formanufacturing a light emitting element, it is preferable that theorganometallic complex be dissolved in a solvent at a concentration ofequal to or higher than 0.6 g/L, more preferably, the concentration beequal to or higher than 0.9 g/L.

In addition, it is preferable that the solvent be an organic solventhaving a boiling point of equal to or greater than 50° C. and equal toor less than 200° C. because the solvent needs to be removed for filmformation, in consideration of using the above-described composition formanufacturing a light emitting element.

In addition, in consideration of using the composition for manufacturinga light emitting element, it is preferable that the compositiondescribed in this embodiment mode further include an organicsemiconductor material. As the organic semiconductor material, anaromatic compound or a heteroaromatic compound which is solid at roomtemperature can be used. Although a low molecular compound or a highmolecular compound can be used as the organic semiconductor material, ahigh molecular compound is particularly preferable in terms of thequality of a film which is formed. When a low molecular compound isused, a low molecular compound (which may be referred to as a mediummolecular compound) including a substituent which can increase thesolubility in a solvent is preferably used.

Specific examples of the organic semiconductor material are listedbelow. Examples of an organic semiconductor material having ahole-transporting property, which can be used, are a low molecularcompound such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbr.:NPB), 4,4′-bis[N-(9-phenanthryl)-N-phenylamino]biphenyl (abbr.: PPB),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbr.: TPD),4,4′-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl (abbr.:DFLDPBi), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbr.: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbr.:m-MTDATA), 4,4′,4″-tri(N-carbazolyl)triphenylamine (abbr.: TCTA),1,1-bis[4-(diphenylamino)phenyl]cyclohexane (abbr.: TPAC),9,9-bis[4-(diphenylamino)phenyl]fluorene (abbr.: TPAF),N-[4-(9-carbazolyl)phenyl]-N-phenyl-9,9-dimethylfluoren-2-amine (abbr.:YGAF), 4,4′-di(N-carbazolyl)biphenyl (abbr.: CBP),1,3-bis(N-carbazolyl)benzene (abbr.: mCP), or1,3,5-tris(N-carbazolyl)benzene (abbr.: TCzB); and a high molecularcompound such as poly(4-vinyltriphenylamine) (abbr.: PVTPA) orpoly(N-vinylcarbazole) (abbr.: PVK). As an organic semiconductormaterial having an electron-transporting property, a low molecularcompound such as 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]carbazole(abbr.: CO11),1,3-bis[5-p-tert-buthylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbr.:OXD-7), 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbr.:PBD), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbr.: TPBI),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole (abbr.:TAZ01),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbr.: p-EtTAZ), 9,9′,9″-[1,3,5-triazine-2,4,6-triyl]tricarbazole(abbr.: TCzTRZ),2,2′,2″-(1,3,5-benzenetriyl)tris(6,7-dimethyl-3-phenylquinoxaline)(abbr.: TriMeQn),9,9′-(quinoxaline-2,3-diyldi-4,1-phenylene)di(9H-carbazole) (abbr.:CzQn),3,3′,6,6′-tetraphenyl-9,9′-(quinoxaline-2,3-diyldi-4,1-phenylene)di(9H-carbazole)(abbr.: DCzPQ), bathophenanthroline (abbr.: BPhen), bathocuproine(abbr.: BCP),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbr.:BAlq),tris[2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazolato]aluminum(III)(abbr.: Al(OXD)₃),tris(2-hydroxyphenyl-1-phenyl-1H-benzimidazolato)aluminum(III) (abbr:Al(BIZ)₃), bis[2-(2-hydroxyphenyl)benzothiazolato]zinc(II) (abbr.:Zn(BTZ)₂), or bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(II) (abbr.:Zn(PBO)₂); poly(2,5-pyridine-diyl) (abbr.: PPy); or a metal complex highmolecular compound disclosed in the following reference can be used(reference: X. T. TAO et al., Applied Physics Letters, vol. 70, No. 12,24 Mar. 1997, pages 1503-1505).

The composition may further include a binder in order to improve thequality of a film which is formed. A high molecular compound that iselectrically inactive is preferably used as the binder. Specifically,polymethylmethacrylate (abbr.: PMMA), polyimide, or the like can beused.

The composition described in this embodiment mode includes anorganometallic complex which is dissolved and is preferably used formanufacturing a light emitting element. The composition has anorganometallic complex dissolved at a sufficiently high concentrationfor forming a film including the organometallic complex, and thus thecomposition is preferably used especially for manufacturing a lightemitting element.

In addition, the composition described in this embodiment mode includesan organometallic complex including a pyrazine skeleton, which iscapable of highly efficient light emission. Thus, the composition issuitable for manufacturing a light emitting element having excellentcharacteristics.

When a composition including alcohol as a solvent is used inmanufacturing a light emitting element, EL layers of the light emittingelement can be stacked. In other words, a layer can be further formedusing a composition which includes alcohol as a solvent over a layerincluding an organic compound which is formed by an evaporation methodor the like. Thus, light emitting elements having excellentcharacteristics can be manufactured.

Embodiment Mode 2

One mode of a light emitting element using an organometallic complex ofthe present invention or a composition of the present invention, and amethod for manufacturing the light emitting element is described belowwith reference to FIG. 1.

Note that in this specification, composite refers not only to a simplemixture of two kinds of materials, but also to a mixture of pluralmaterials in which charges are given and received between materials.

A light emitting element of the present invention includes a pluralityof layers between a pair of electrodes. The plurality of layers arestacked layers of a substance having a high carrier-injecting propertyand of a substance having a high carrier-transporting property. Thoselayers are stacked so that a light emitting region is formed away fromthe electrodes. That is, they are stacked so that carriers arerecombined in an area away from the electrodes.

In FIG. 1, a substrate 100 is used as a support base of a light emittingelement. For example, glass, plastic, or the like may be used as thesubstrate 100. Any material other than those may be used as long as thematerial serves as a support base of the light emitting element.

In this embodiment mode, the light emitting element includes a firstelectrode 101, a second electrode 102, and an EL layer 103 between thefirst electrode 101 and the second electrode 102. In this embodimentmode, the following description is made assuming that the firstelectrode 101 serves as an anode and the second electrode 102 serves asa cathode. In other words, in the description below, it is assumed thatlight is emitted when voltage is applied to the first electrode 101 andthe second electrode 102 in a manner such that the potential of thefirst electrode 101 is higher than that of the second electrode 102.

It is preferable that the first electrode 101 be formed using a metal,an alloy, or a conductive compound with a high work function(specifically, equal to or greater than 4.0 eV), a mixture thereof, orthe like. Specifically, indium tin oxide (ITO), indium tin oxidecontaining silicon or silicon oxide, indium zinc oxide (IZO), indiumoxide containing tungsten oxide and zinc oxide (IWZO), or the like canbe used. A film of such conductive metal oxide is typically formed bysputtering, but may be formed by application of a sol-gel process or thelike. For example, a film of indium zinc oxide (IZO) can be formed by asputtering method using a target in which zinc oxide is added to indiumoxide at 1 to 20 wt %. A film of indium oxide containing tungsten oxideand zinc oxide (IWZO) can be formed by a sputtering method using atarget in which tungsten oxide and zinc oxide are added to indium oxideat 0.5 to 5 wt % and 0.1 to 1 wt %, respectively. Further, gold (Au),platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum(Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), nitride of ametal material (e.g., titanium nitride), or the like can be used.

When a layer including a composite material which is described later isused as a layer in contact with the first electrode 101, the firstelectrode 101 can be formed using any of a variety of metals, alloys,conductive compounds, a mixture thereof, or the like regardless of theirwork function. For example, aluminum (Al), silver (Ag), an aluminumalloy (AlSi), or the like can be used. Alternatively, an elementbelonging to Group 1 or Group 2 of the periodic table, which is alow-work function material, that is, an alkali metal such as lithium(Li) or cesium (Cs), an alkaline earth metal such as magnesium (Mg),calcium (Ca), or strontium (Sr), or an alloy thereof (MgAg or AlLi); arare earth metal such as europium (Eu) or ytterbium (Yb), or an alloythereof; or the like can be used. A film including an alkali metal, analkaline earth metal, or an alloy thereof can be formed by a vacuumevaporation method. Alternatively, a film including an alloy of analkali metal or an alkaline earth metal can be formed by a sputteringmethod. Further alternatively, the film can be formed using a silverpaste or the like by a droplet discharge method or the like.

There is no particular limitation on a stacked structure of the EL layer103. It is acceptable as long as the EL layer 103 is formed ofappropriate combination including the light emitting layer described inthis embodiment mode and a layer including a substance having a highelectron-transporting property, a substance having a highhole-transporting property, a substance having a high electron-injectingproperty, a substance having a high hole-injecting property, a bipolarsubstance (a substance having a high electron-transporting andhole-transporting property), or the like. For example, appropriatecombination of a hole-injecting layer, a hole-transporting layer, alight emitting layer, an electron-transporting layer, anelectron-injecting layer, and the like can be employed. Examples ofmaterials for those layers are described below.

A hole-injecting layer 111 is a layer including a substance having ahigh hole-injecting property. As a substance having a highhole-injecting property, molybdenum oxide, vanadium oxide, rutheniumoxide, tungsten oxide, manganese oxide, or the like can be used.Alternatively, the hole-injecting layer 111 can be formed of aphthalocyanine-based compound such as phthalocyanine (abbr.: H₂Pc) orcopper phthalocyanine (abbr.: CuPc), a high molecular compound such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS),or the like.

Alternatively, the hole-injecting layer 111 can be formed using acomposite material in which an acceptor substance is mixed into asubstance having a high hole-transporting property. Note that a materialfor forming the electrode can be selected regardless of its workfunction if the composite material in which an acceptor substance ismixed into a substance having a high hole-transporting property is used.In other words, not only a high-work function material, but also alow-work function material can be used for the first electrode 101.Examples of the acceptor substance are7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbr.: F₄-TCNQ),chloranil, transition metal oxide, and oxide of a metal belonging toGroup 4 to Group 8 of the periodic table. Specifically, vanadium oxide,niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,tungsten oxide, manganese oxide, and rhenium oxide are preferably usedbecause of their high electron-accepting property. In particular,molybdenum oxide is preferable because of its stability in theatmosphere, low hygroscopic property, and easiness of handling.

As the substance having a high hole-transporting property which is usedfor the composite material, any of a variety of compounds such as anaromatic amine compound, a carbazole derivative, aromatic hydrocarbon,or a high molecular compound (e.g., an oligomer, a dendrimer, or apolymer) can be used. A substance having a hole mobility of equal to orgreater than 10⁻⁶ cm²/Vs is preferably used as the substance having ahigh hole-transporting property which is used for the compositematerial. Note that any substance other than the above substances may beused as long as it is a substance in which the hole-transportingproperty is higher than the electron-transporting property. Organiccompounds that can be used for the composite material are specificallylisted below.

Examples of the aromatic amine compound which can be used for thecomposite material areN,N′-bis(4-methylphenyl)(p-tolyl)-N,N′-diphenyl-p-phenylenediamine(abbr.: DTDPPA),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbr.: DPAB),4,4′-bis(N-{4-[N′-(3-methylphenyl)-N-phenylamino]phenyl}-N-phenylamino)biphenyl(abbr.: DNTPD),1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbr.:DPA3B), and the like.

Examples of the carbazole derivative which can be used for the compositematerial are3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbr.:PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbr.: PCzPCA2),3-[N-(1-naphtyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbr.: PCzPCN1), and the like.

Examples of the carbazole derivative which can be used for the compositematerial are 4,4′-di(N-carbazolyl)biphenyl (abbr.: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbr.: TCPB),9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbr.: CzPA),1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, and thelike.

Examples of the aromatic hydrocarbon which can be used for the compositematerial are 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbr.:t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene,9,10-bis(3,5-diphenylphenyl)anthracene (abbr.: DPPA),2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbr.: t-BuDBA),9,10-di(2-naphthyl)anthracene (abbr.: DNA), 9,10-diphenylanthracene(abbr.: DPAnth), 2-tert-butylanthracene (abbr.: t-BuAnth),9,10-bis(4-methyl-1-naphthyl)anthracene (abbr.: DMNA),9,10-bis[2-(1-naphthyl)phenyl]-2-tert-butyl-anthracene,9,10-bis[2-(1-naphthyl)phenyl]anthracene,2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene,2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl,10,10′-diphenyl-9,9′-bianthryl,10,10′-bis(2-phenylphenyl)-9,9′-bianthryl,10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene,tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, andthe like. Further, pentacene, coronene, or the like can be used. Thus,an aromatic hydrocarbon having a hole mobility of equal to or greaterthan 1×10⁻⁶ cm²/Vs and having 14 to 42 carbon atoms is preferable.

Note that the aromatic hydrocarbon which can be used for the compositematerial may have a vinyl skeleton. Examples of the aromatic hydrocarbonhaving a vinyl skeleton are 4,4′-bis(2,2-diphenylvinyl)biphenyl (abbr.:DPVBi) 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbr.: DPVPA),and the like.

For the hole-injecting layer 111, a high molecular compound (anoligomer, a dendrimer, or a polymer) can be used. For example, a highmolecular compound such as poly(N-vinylcarbazole) (abbr.: PVK),poly(4-vinyltriphenylamine) (abbr.: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbr.: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbr.:Poly-TPD) can be used. Alternatively, a high molecular compound mixedwith acid, such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonicacid) (PEDOT/PSS) or polyaniline/poly(styrenesulfonic acid) (PAni/PSS)can be used.

Note that the hole-injecting layer 111 can be formed using a compositematerial of the above-described high molecular compound, such as PVK,PVTPA, PTPDMA, or Poly-TPD, and the above-described acceptor substance.

A hole-transporting layer 112 includes a substance having a highhole-transporting property. An example of the substance having a highhole-transporting property is an aromatic amine compound such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbr.: NPB or α-NPB),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbr: TPD), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbr.:TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbr.: MTDATA), or4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl (abbr.:BSPB). Most of these substances mentioned here have a hole mobility ofequal to or greater than 10⁻⁶ cm²/Vs. Note that any substance other thanthe above-mentioned substances may also be used as long as it is asubstance in which the hole-transporting property is higher than theelectron-transporting property. The layer including a substance having ahigh hole-transporting property is not limited to a single layer, andmay be a stack of two or more layers each including the above-mentionedsubstance.

For the hole-transporting layer 112, a high molecular compound such asPVK, PVTPA, PTPDMA, or Poly-TPD can be used alternatively.

A light emitting layer 113 includes a substance having a high lightemitting property. An organometallic complex of the present inventionwhich is described in Embodiment Mode 1 can be used as the substancehaving a high light emitting property. An organometallic complex of thepresent invention can be preferably used as a light emitting substanceof a light emitting element because of its high light emissionefficiency.

In the light emitting layer 113, a structure in which an organometalliccomplex of the present invention is dispersed in a host material isparticularly preferable. As the host material, an organic semiconductormaterial having a hole-transporting property mentioned in EmbodimentMode 1 (e.g., NPB, PPB, TPD, DFLDPBi, TDATA, m-MTDATA, TCTA, TPAC, TPAF,YGAF, CBP, mCP, TCzB, PVTPA, or PVK); an organic semiconductor materialhaving an electron-transporting property (e.g., CO11, OXD-7, PBD, TPBI,TAZ01, p-EtTAZ, TCzTRZ, TriMeQn, CzQn, DCzPQ, BPhen, BCP, BAlq,Al(OXD)₃, Al(BIZ)₃, Zn(BTZ)₂, Zn(PBO)₂, or PPy); or a metal complex highmolecular compound disclosed in the following reference (reference: X.T. TAO et al., Applied Physics Letters, vol. 70, No. 12, 24 Mar. 1997,pages 1503-1505); or the like can be used. Further, it is preferablethat both an organic semiconductor material having a hole-transportingproperty and an organic semiconductor material having anelectron-transporting property, which are mentioned above, be used as ahost material, in order to improve the lifetime of an element.

The light emitting layer 113 can be formed by various methods, whetherit is a dry process or a wet process. For example, the light emittinglayer 113 can be formed by an evaporation method, which is a dryprocess. Alternatively, the light emitting layer 113 can be formed by awet process using a composition including an organometallic complex ofthe present invention which is described in Embodiment Mode 1.Specifically, the composition described in Embodiment Mode 1 may beapplied by a droplet discharge method, a spin coating method, or thelike, and then, the solvent may be removed. A heat treatment, a lowpressure treatment, a heat treatment under low pressure, or the like isemployed for removing the solvent.

Here, it is preferable that the solvent included in the composition bealcohol for the following reason. Low molecular compounds which are usedfor light emitting elements are generally difficult to be dissolved inalcohol. Therefore, when the solvent included in the composition isalcohol, even if a layer including a low molecular compound which isformed by an evaporation method or the like is formed before formationof a light emitting layer, the light emitting layer can be stackedthereon by application of the composition by a wet process.

An electron-transporting layer 114 includes a substance having a highelectron-transporting property. For example, the electron-transportinglayer 114 can be formed using a metal complex or the like having aquinoline or benzoquinoline skeleton, such astris(8-quinolinolato)aluminum (abbr.: Alq),tris(4-methyl-8-quinolinolato)aluminum (abbr.: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbr: BeBq₂), orbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbr.: BAlq).Alternatively, a metal complex or the like having an oxazole-based orthiazole-based ligand, such as bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(abbr.: Zn(BOX)₂) or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbr.:Zn(BTZ)₂) can be used. As an alternative to the metal complex,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbr.: PBD),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbr.:OXD-7), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbr.: TAZ), bathophenanthroline (abbr.: BPhen), bathocuproine (abbr.:BCP), or the like can be used. Most of these substances mentioned herehave an electron mobility of equal to or greater than 10⁻⁶ cm²/Vs. Notethat any substance other than the above substances may be used as longas it is a substance in which the electron-transporting property ishigher than the hole-transporting property. The electron-transportinglayer is not limited to a single layer, and may be a stack of two ormore layers each including the above-mentioned substance.

Further, a high molecular compound such aspoly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbr.:PF-Py) orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbr.: PF-BPy) can be used for the electron-transporting layer 114.

An electron-injecting layer 115 may be provided. The electron-injectinglayer 115 can be formed using an alkali metal compound or an alkalineearth metal compound such as lithium fluoride (LiF), cesium fluoride(CsF), or calcium fluoride (CaF₂). Further, a layer, in which asubstance having an electron-transporting property and an alkali metalor an alkaline earth metal are combined can be employed as theelectron-injecting layer 115. For example, a layer of Alq in whichmagnesium (Mg) is included can be used. Note that it is more preferableto use a layer in which a substance having an electron-transportingproperty and an alkali metal or an alkaline earth metal are combined asthe electron-injecting layer, because electrons are injected from thesecond electrode 102 efficiently.

A substance forming the second electrode 102 can be a metal, an alloy,or a conductive compound, which has a low work function (specifically,equal to or less than 3.8 eV), a mixture thereof, or the like. Specificexamples of such cathode materials are an element belonging to Group 1or Group 2 of the periodic table, that is an alkali metal such aslithium (Li) or cesium (Cs) or an alkaline earth metal such as magnesium(Mg), calcium (Ca), and strontium (Sr); an alloy thereof (e.g., MgAg orAlLi); a rare earth metal such as europium (Eu) or ytterbium (Yb), analloy thereof; or the like. A film including an alkali metal, analkaline earth metal, or an alloy thereof can be formed by a vacuumevaporation method. Alternatively, a film of an alkali metal, analkaline earth metal, or an alloy thereof can be formed by a sputteringmethod. Further alternatively, a film can be formed using a silver pasteor the like by a droplet discharge method or the like.

When the electron-injecting layer 115 is provided between the secondelectrode 102 and the electron-transporting layer 114, any of a varietyof conductive materials such as Al, Ag, ITO, or indium tin oxidecontaining silicon or silicon oxide can be used for the second electrode102 regardless of its work function. A film of such a conductivematerial can be formed by a sputtering method, a droplet dischargemethod, a spin coating method, or the like.

In the light emitting element having the above-described structure inthis embodiment mode, application of voltage between the first electrode101 and the second electrode 102 makes current flow, whereby holes andelectrons are recombined in the light emitting layer 113 including asubstance having a high light emitting property and light is emitted.That is, a light emitting region is formed in the light emitting layer113.

Light which is emitted is extracted outside through either one or boththe first electrode 101 and the second electrode 102. Accordingly,either one or both the first electrode 101 and the second electrode 102are formed of a light-transmissive material. When only the firstelectrode 101 is a light-transmissive electrode, light is extracted fromthe substrate side through the first electrode 101. When only the secondelectrode 102 is a light-transmissive electrode, light is extracted froma side opposite to the substrate side through the second electrode 102.When both of the first electrode 101 and the second electrode 102 arelight-transmissive electrodes, light is extracted from both thesubstrate side and the side opposite to the substrate side through thefirst electrode 101 and the second electrode 102.

Note that while FIG. 1 shows a structure in which the first electrode101 which serves as an anode is disposed on the substrate 100 side, thesecond electrode 102 which serves as a cathode may be disposed on thesubstrate 100 side. FIG. 2 shows a structure in which the secondelectrode 102 which serves as a cathode, the EL layer 103, and the firstelectrode 101 which serves as an anode are stacked in that order overthe substrate 100. In the EL layer 103, the layers are stacked in thereverse order of the order shown in FIG. 1.

The EL layer can be formed by various methods, whether it is a dryprocess or a wet process. A film forming method for forming electrodesand layers may be different between the electrodes and layers. A vacuumevaporation method, a sputtering method, or the like can be given as adry process. A droplet discharge method, a spin coating method, or thelike can be given as a wet process.

For example, the EL layer may be formed of a high molecular compoundamong the above-described materials by a wet process. The EL layer canalternatively be formed of a low molecular compound by a wet process.Further alternatively, the EL layer may be formed of a low molecularorganic compound by a dry process such as a vacuum evaporation method.

Although the light emitting layer 113 can be formed by various methods,whether it is a dry process or a wet process, the light emitting layer113 can be preferably formed of the composition described in EmbodimentMode 1 by a wet process. Specifically, the composition described inEmbodiment Mode 1 may be applied by a droplet discharge method, a spincoating method, or the like, and then, the solvent may be removed. Aheat treatment, a low pressure treatment, a heat treatment under lowpressure, or the like is employed for removing the solvent. The materialuse efficiency can be improved by employing a wet process, thus themanufacturing cost of light emitting element can be reduced.

The electrodes may also be formed by a wet process such as a sol-gelprocess or by a wet process using a metal paste. Alternatively, theelectrodes may be formed by a dry process such as a sputtering method ora vacuum evaporation method.

When the light emitting element described in this embodiment mode isapplied to a display device and the light emitting layer in the lightemitting element is selectively formed according to each color, thelight emitting layer is preferably formed by a wet process. When thelight emitting layer is formed by a droplet discharge method, selectiveformation of the light emitting layer for each color can be easilyperformed even in the case of a large substrate, and thus productivityis improved.

A specific method for forming the light emitting element is describedbelow.

For example, the structure shown in FIG. 1 may be obtained by thefollowing steps: forming the first electrode 101 by a sputtering method,which is a dry process; forming the hole-injecting layer 111 by adroplet discharge method or a spin coating method, which is a wetprocess; forming the hole-transporting layer 112 by a vacuum evaporationmethod, which is a dry process; forming the light emitting layer 113 bya droplet discharge method, which is a wet process; forming theelectron-transporting layer 114 by a vacuum evaporation method, which isa dry process; forming the electron-injecting layer 115 by a vacuumevaporation method, which is a dry process; and forming the secondelectrode 102 by a droplet discharge method or a spin coating methodwhich is a wet process. Alternatively, the structure shown in FIG. 1 maybe obtained by the following steps: forming the first electrode 101 by adroplet discharge method, which is a wet process; forming thehole-injecting layer 111 by a vacuum evaporation method, which is a dryprocess; forming the hole-transporting layer 112 by a droplet dischargemethod or a spin coating method, which is a wet process; forming thelight emitting layer 113 by a droplet discharge method, which is a wetprocess; forming the electron-transporting layer 114 by a dropletdischarge method or a spin coating method, which is a wet process;forming the electron-injecting layer 115 by a droplet discharge methodor a spin coating method, which is a wet process; and forming the secondelectrode 102 by a droplet discharge method or a spin coating method,which is a wet process. Note that the method is not limited to theabove-described methods, and a method in which a wet process and a dryprocess are combined as appropriate may be employed.

For example, the structure shown in FIG. 1 can be obtained by thefollowing steps: forming the first electrode 101 by a sputtering method,which is a dry process; forming the hole-injecting layer 111 and thehole-transporting layer 112 by a droplet discharge method or a spincoating method, which is a wet process; forming the light emitting layer113 by a droplet discharge method, which is a wet process; forming theelectron-transporting layer 114 and the electron-injecting layer 115 bya vacuum evaporation method, which is a dry process; and forming thesecond electrode 102 by a vacuum evaporation method, which is a dryprocess. In other words, it is possible to form the hole-injecting layer111 to the light emitting layer 113 by a wet process and to form theelectron-transporting layer 114 to the second electrode 102 thereover bya dry process over the substrate provided with the first electrode 101which has already been formed in a desired shape. By this method, thehole-injecting layer 111 to the light emitting layer 113 can be formedat atmospheric pressure and the light emitting layer 113 can beselectively formed according to each color with ease. In addition, theelectron-transporting layer 114 to the second electrode 102 can besuccessively formed in vacuum. Therefore, the process can be simplified,and productivity can be improved.

The process is exemplarily described below. A film of PEDOT/PSS isformed as the hole-injecting layer 111 over the first electrode 101.Since PEDOT/PSS is soluble in water, a film thereof can be formed usingan aqueous solution of PEDOT/PSS by a spin coating method, a dropletdischarge method, or the like. The hole-transporting layer 112 is notprovided and the light emitting layer 113 is provided over thehole-injecting layer 111. The light emitting layer 113 can be formed bya droplet discharge method, using the composition which is described inEmbodiment Mode 1, including a solvent (e.g., toluene, eylene,dodecylbenzene, a mixed solvent of dodecylbenzene and tetralin, ethers,or alcohols) which does not dissolve the hole-injecting layer 111(PEDOT/PSS) which has already been formed. Next, theelectron-transporting layer 114 is formed over the light emitting layer113. When the electron-transporting layer 114 is formed by a wetprocess, the electron-transporting layer 114 should be formed using asolvent which does not dissolve the hole-injecting layer 111 and thelight emitting layer 113 which have already been formed. In that case,the selection range of solvents is limited; therefore, a dry process iseasier. Thus, by successively forming the electron-transporting layer114 to the second electrode 102 in vacuum by a vacuum evaporationmethod, which is a dry process, the manufacturing process can besimplified.

Meanwhile, a structure shown in FIG. 2 can be formed in the reverseorder of the above-described steps: forming the second electrode 102 bya sputtering method or a vacuum evaporation method, which is a dryprocess; forming the electron-injecting layer 115 and theelectron-transporting layer 114 by a vacuum evaporation method, which isa dry process; forming the light emitting layer 113 by a dropletdischarge method, which is a wet process; forming the hole-transportinglayer 112 and the hole-injecting layer 111 by a droplet discharge methodor a spin coating method, which is a wet process; and forming the firstelectrode 101 by a droplet discharge method or a spin coating method,which is a wet process. By this method, the second electrode 102 to theelectron-transporting layer 114 can be successively formed in vacuum bya dry process, and the light emitting layer 113 to the first electrode101 can be formed at atmospheric pressure. Therefore, the manufacturingprocess can be simplified, and productivity can be improved. Thecomposition described in Embodiment Mode 1 can be applied to a layerformed by an evaporation method or the like, which allows the abovedescribed manufacturing method.

Note that the light emitting element is formed over a substrate ofglass, plastic, or the like in this embodiment mode. When a plurality ofsuch light emitting elements are formed over a substrate, a passivematrix light emitting device can be manufactured. It is possible toform, for example, thin film transistors (TFTs) over a substrate formedof glass, plastic, or the like and form light emitting elements overelectrodes that are electrically connected to the TFTs. In that case, anactive matrix light emitting device in which drive of the light emittingelements is controlled by TFTs can be manufactured. Note that there isno particular limitation on the structure of TFTs, and either staggeredTFTs or inversely staggered TFTs may be employed. In addition, a drivercircuit formed over a TFT substrate may include both n-channel andp-channel TFTs or either n-channel or p-channel TFTs. Further, there isno particular limitation on the crystallinity of a semiconductor filmwhich is used for TFTs, and either an amorphous semiconductor film or acrystalline semiconductor film may be used.

Since a light emitting element of the present invention includes anorganometallic complex which is capable of efficient light emission, thelight emission efficiency is high.

When a light emitting element is formed using the composition describedin Embodiment Mode 1, selective formation of the light emitting layerfor each color can be easy even in the case of a large substrate, andthus productivity is improved. Accordingly, the method for manufacturinga light emitting element, which is described in this embodiment mode isexcellent in mass productivity. Also, the manufacturing cost can bereduced.

Embodiment Mode 3

In this embodiment mode, a mode of a light emitting element in which aplurality of light emitting units according to the present invention arestacked (hereinafter, referred to as a stacked-type element) isdescribed with reference to FIG. 3. This light emitting element is astacked-type light emitting element including a plurality of lightemitting units between a first electrode and a second electrode. Thisstructure of the light emitting unit can be similar to that of the ELlayer described in Embodiment Mode 2. In other words, a light emittingelement including one light emitting unit is described in EmbodimentMode 2, and a light emitting element including a plurality of lightemitting units is described in this embodiment mode.

In FIG. 3, a first light emitting unit 511, a charge generation layer513, and a second light emitting unit 512 are stacked between a firstelectrode 501 and a second electrode 502. The first electrode 501 andthe second electrode 502 can be similar to the electrodes in EmbodimentMode 2. The structures of the first light emitting unit 511 and thesecond light emitting unit 512 may be the same or different. Thestructure can be similar to that described in Embodiment Mode 2.

The charge generation layer 513 includes a composite material of anorganic compound and metal oxide. This composite material of an organiccompound and metal oxide has been described in Embodiment Mode 2 andincludes an organic compound and metal oxide such as vanadium oxide,molybdenum oxide, or tungsten oxide. As the organic compound, any of avariety of compounds such as an aromatic amine compound, a carbazolederivative, aromatic hydrocarbon, or a high molecular compound (e.g., anoligomer, a dendrimer, or a polymer) can be used. A substance having ahole mobility of equal to or greater than 10⁻⁶ cm²/Vs is preferably usedas the organic compound. Note that any substance other than the abovesubstances may be used as long as it is a substance in which thehole-transporting property is higher than the electron-transportingproperty. The composite material of an organic compound and metal oxideis excellent in carrier-injecting property and carrier-transportingproperty; therefore, low-voltage driving and low-current driving can beachieved.

Note that the charge generation layer 513 may be formed by combining thecomposite material of an organic compound and metal oxide and a layerincluding any other material. For example, the charge generation layer513 may be formed by a combination of the layer including the compositematerial of an organic compound and metal oxide with a layer includingone compound selected from electron donating substances and a compoundhaving a high electron-transporting property. Alternatively, the chargegeneration layer 513 may be formed by a combination of a transparentconductive film and a layer including the composite material of anorganic compound and metal oxide.

The charge generation layer 513 sandwiched between the first lightemitting unit 511 and the second light emitting unit 512 may have anystructure as long as electrons can be injected to a light emitting uniton one side and holes can be injected to a light emitting unit on theother side when voltage is applied between the first electrode 501 andthe second electrode 502. For example, in FIG. 3, the charge generationlayer 513 injects electrons to the first light emitting unit 511 andinjects holes to the second light emitting unit 512 when voltage isapplied so that the potential of the first electrode is higher than thatof the second electrode.

While the light emitting element having two light emitting units isdescribed in this embodiment mode, the present invention can besimilarly applied to a light emitting element in which three or morelight emitting units are stacked. When a plurality of light emittingunits are arranged between a pair of electrodes so that two of the lightemitting units are partitioned with a charge generation layer, like thelight emitting element according to this embodiment mode, high luminanceemission can be realized at a low current density, thus, a long-lifelight emitting element can be realized. When the light emitting elementis applied to a lighting device, voltage drop due to resistance of theelectrode materials can be suppressed, and thus uniform light emissionover a large area can be realized. Furthermore, a light emitting devicewhich can drive at a low voltage and consumes low power can be achieved.

When emission colors are different between the light emitting units,light emission of a desired color can be obtained from the lightemitting element as a whole. For example, when a light emitting elementhas two light emitting units in which an emission color of the firstlight emitting unit and an emission color of the second light emittingunit are complementary colors, it is possible to obtain a light emittingelement emitting white light as a whole. Note that the complementarycolors refer to colors that can produce an achromatic color when theyare mixed. That is, white light emission can be obtained by mixture oflight from substances, of which the light emission colors arecomplementary colors. This is similarly applied to a light emittingelement having three light emitting units. For example, white lightemission can be obtained from the light emitting element as a whole whenemission colors of the first, second, and third light emitting units arered, green, and blue, respectively.

This embodiment mode can be combined with any other embodiment mode asappropriate.

Embodiment Mode 4

In this embodiment mode, a light emitting device including a lightemitting element of the present invention is described.

In this embodiment mode, a light emitting device including the lightemitting element of the present invention in the pixel portion isdescribed with reference to FIGS. 4A and 4B. Note that FIG. 4A is a topview of a light emitting device, and FIG. 4B is a cross-sectional viewtaken along lines A-A′ and B-B′ in FIG. 4A. This light emitting deviceincludes a driver circuit portion (a source side driver circuit) 601, apixel portion 602, and a driver circuit portion (a gate side drivercircuit) 603, which are indicated by dotted lines, to control lightemission from light emitting elements. Reference numeral 604 denotes asealing substrate, reference numeral 605 denotes a sealant, and aportion surrounded by the sealant 605 is a space 607.

Note that a lead wiring 608 is a wiring for transmitting signals whichare input to the source side driver circuit 601 and the gate side drivercircuit 603. The lead wiring 608 receives video signals, clock signals,start signals, reset signals, and the like from a flexible printedcircuit (FPC) 609, which is an external input terminal. Although onlythe FPC is shown in FIGS. 4A and 4B, the FPC may be provided with aprinted wiring board (PWB). The category of the light emitting device inthis specification includes not only a light emitting device itself butalso a light emitting device attached with a FPC or a PWB.

Next, a cross-sectional structure is described with reference to FIG.4B. Although the driver circuit portion and the pixel portion are formedover an element substrate 610, FIG. 4B shows the source side drivercircuit 601, which is one of the driver circuit portions and one pixelin the pixel portion 602.

A CMOS circuit, which is a combination of an n-channel TFT 623 and ap-channel TFT 624, is formed as the source side driver circuit 601. Eachdriver circuit portion may be any of a variety of circuits such as aCMOS circuit, a PMOS circuit, or an NMOS circuit. While a driverintegration type in which a driver circuit is formed over a substrateprovided with a pixel portion is described in this embodiment mode, adriver circuit is not necessarily formed over a substrate provided witha pixel portion, a driver circuit can be formed outside the substrate.

The pixel portion 602 has a plurality of pixels each including aswitching TFT 611, a current control TFT 612, and a first electrode 613which is electrically connected to a drain of the current control TFT612. An insulator 614 is formed so as to cover an end portion of thefirst electrode 613. In this case, the insulator 614 is formed using apositive photosensitive acrylic resin film.

The insulator 614 is formed to have a curved surface having a curvatureat an upper end portion or a lower end portion in order to make thecoverage favorable. For example, in the case of using positivephotosensitive acrylic as a material for the insulator 614, it ispreferable that the insulator 614 be formed so as to have a curvedsurface with a curvature radius (0.2 μm to 3 μm) only at the upper endportion. The insulator 614 can be formed using either a negative typewhich becomes insoluble in an etchant by light irradiation or a positivetype which becomes soluble in an etchant by light irradiation.

An EL layer 616 and a second electrode 617 are formed over the firstelectrode 613. The first electrode 613 can be formed using any of avariety of metals, alloys, and conductive compounds, a mixture thereof,or the like. When the first electrode serves as an anode, it ispreferable that the first electrode be formed using a metal, an alloy,or a conductive compound with a high work function (a work function ofequal to or higher than 4.0 eV), or a mixture thereof. For example, thefirst electrode 613 can be formed using a single-layer film like anindium tin oxide film containing silicon, an indium zinc oxide film, atitanium nitride film, a chromium film, a tungsten film, a Zn film, or aPt film; or a stacked film, such as a stack of a titanium nitride filmand a film containing aluminum as its main component, or a three-layerstructure of a titanium nitride film, a film containing aluminum as itsmain component, and a titanium nitride film. Note that when the firstelectrode 613 has a stacked structure, it can have low resistance as awiring, form a favorable ohmic contact, and serve as an anode.

The EL layer 616 includes the organometallic complex described inEmbodiment mode 1. The EL layer 616 is formed by any of a variety ofmethods such as an evaporation method using an evaporation mask using anevaporation mask, a droplet discharge method, or a spin coating method.Either low molecular compounds or high molecular compounds (e.g., anoligomer or a dendrimer) may be used as a material for forming the ELlayer 616. Note that, not only an organic compound but also an inorganiccompound may be used as the material used for the EL layer.

The second electrode 617 can be formed using any of a variety of metals,alloys, and conductive compounds, a mixture thereof, and the like. Whenthe second electrode serves as a cathode, it is preferable that thesecond electrode be formed using any of a metal, an alloy, and aconductive compound with a low work function (a work function of equalto or less than 3.8 eV or lower), or a mixture thereof. Examples thereofare elements belonging to Group 1 or Group 2 of the periodic table, thatis, alkali metals such as lithium (Li) and cesium (Cs) andalkaline-earth metals such as magnesium (Mg), calcium (Ca), andstrontium (Sr), alloys thereof (MgAg or AlLi), and the like. Note thatwhen light emitted from the EL layer 616 is transmitted through thesecond electrode 617, the second electrode 617 can be formed using astack of a metal thin film with a reduced thickness and a transparentconductive film (e.g., a film of indium tin oxide (ITO), indium tinoxide containing silicon or silicon oxide, indium zinc oxide (IZO), orindium oxide containing tungsten oxide and zinc oxide (IWZO)).

The sealing substrate 604 is attached to the element substrate 610 withthe sealant 605; thus, a light emitting element 618 is in the space 607surrounded by the element substrate 610, the sealing substrate 604, andthe sealant 605. The space 607 is filled with a filler such as an inertgas (e.g., nitrogen or argon) or the sealant 605.

It is preferable that the sealant 605 be an epoxy-based resin and amaterial of the sealant 605 permeate little moisture and oxygen as muchas possible. As the sealing substrate 604, a plastic substrate made offiberglass-reinforced plastics (FRP), polyvinyl fluoride (PVF),polyester, acrylic, or the like can be used as an alternative to a glasssubstrate or a quartz substrate.

Accordingly, the light emitting device having the light emitting elementof the present invention can be obtained.

Since a light emitting device of the present invention has a lightemitting element with high light emission efficiency, power consumptionis reduced.

Since a light emitting device of the present invention can be formedusing the composition described in Embodiment Mode 1, the light emittingdevice is excellent in mass productivity. Also, the manufacturing costis reduced because of high use efficiency of the material, whereby a lowcost light emitting device can be obtained.

Although an active matrix light emitting device in which driving of alight emitting element is controlled by a transistor is described inthis embodiment mode, the light emitting device may be a passive matrixlight emitting device. Note that FIGS. 5A and 5B show a passive matrixlight emitting device to which the present invention is applied. FIG. 5Ais a perspective view of the light emitting device, and FIG. 5B is across-sectional view taken along line X-Y in FIG. 5A. In FIGS. 5A and5B, an EL layer 955 is provided between an electrode 952 and anelectrode 956 over a substrate 951. End portions of the electrode 952are covered with an insulating layer 953. Then, a partition layer 954 isprovided over the insulating layer 953. A side wall of the partitionlayer 954 slopes so that the distance between one side wall and theother side wall becomes narrow toward the substrate surface. In otherwords, a cross section taken in the direction of the short side of thepartition layer 954 is trapezoidal, and the base of the cross-section (aside facing in the same direction as a plane direction of the insulatinglayer 953 and in contact with the insulating layer 953) is shorter thanthe upper side of the cross-section (a side facing in the same directionas the plane direction of the insulating layer 953 and not in contactwith the insulating layer 953). A cathode can be patterned by providingthe partition layer 954 in this manner. The passive matrix lightemitting device can also be driven with low power consumption when itincludes a light emitting element having high emission efficiency.

Embodiment Mode 5

In this embodiment mode, one mode is described in which a layer 716including an organometallic complex of the present invention is formedby a droplet discharge method, which is a wet process, with reference toFIGS. 10A to 10D and 11. FIGS. 10A to 10D show a manufacturing steps ofa light-emitting element portion of the light emitting device which isshown in FIGS. 4A and 4B.

In FIG. 10A, a first electrode 713 is formed over an insulating layer719, and an insulating layer 714 is formed so as to cover a part of thefirst electrode 713. Into an exposed portion of the first electrode 713,which is an opening of the insulating layer 714, a droplet 731 isdischarged from a droplet discharge device 730 to form a layer 732containing a composition. The droplet 731 is a composition including anorganometallic complex of the present invention and a solvent and isdeposited onto the first electrode 713 (see FIG. 10B). The solvent isremoved from the layer 732 containing a composition and the layer 732containing a composition is solidified, whereby the layer 716 includingan organometallic complex is formed (see FIG. 10C). The solvent may beremoved by drying or a heating step. In addition, the step ofdischarging the composition may be performed under reduced pressure.

A second electrode 717 is formed over the layer 716 including anorganometallic complex, whereby a light emitting element 718 ismanufactured (see FIG. 10D). While FIGS. 10A to 10D show a structure inwhich only the layer 716 including an organometallic complex is providedbetween the first electrode 713 and the second electrode 717, a layerincluding another material may be provided between the first electrode713 and the layer 716 including an organometallic complex. As isdescribed in Embodiment Mode 1, an organometallic complex of the presentinvention is soluble in alcohol; therefore, when a composition includingalcohol as a solvent is used, EL layers of a light emitting element canbe stacked. Further, a layer including another material may be providedbetween the layer 716 including an organometallic complex and the secondelectrode 717.

When the layer 716 including an organometallic complex is formed by adroplet discharge method as described in this embodiment mode, thecomposition can be selectively discharged in a region in which the layeris to be formed, and accordingly, less material is wasted. In addition,a photolithography process or the like for processing a shape is notneeded, and thus, the process is simplified and the cost can be reduced.

A droplet discharging means which is used in this embodiment mode is ageneral unit to discharge liquid droplets, such as a nozzle equippedwith a composition discharge outlet, a head having one or a plurality ofnozzles.

One mode of a droplet discharging apparatus used for a droplet dischargemethod is shown in FIG. 11. Each of heads 1405 and 1412 of a dropletdischarging means 1403 is connected to a control means 1407, and thiscontrol means 1407 is controlled by a computer 1410; thus, apreprogrammed pattern can be drawn. The timing for dawning may bedetermined, for example, based on a marker 1411 formed over a substrate1400. Alternatively, a reference point may be fixed based on an edge ofthe substrate 1400. The reference point is detected by an imaging means1404 and converted into a digital signal by an image processing means1409. Then, the digital signal is recognized by the computer 1410, andthen, a control signal is generated and transmitted to the control means1407. An image sensor or the like using a charge coupled device (CCD) ora complementary metal oxide semiconductor (CMOS) can be used as theimaging means 1404. Needless to say, information about a pattern to beformed over the substrate 1400 is stored in a storage medium 1408, andthe control signal is transmitted to the control means 1407 based on theinformation, and the head 1405 and the head 1412 of the dropletdischarging means 1403 can be individually controlled based on theinformation. A material to be discharged is supplied to the heads 1405and 1412 from a material supply sources 1413 and 1414 through pipes,respectively.

Inside the head 1405, there are a space filled with a liquid material asindicated by a dotted line 1406 and a nozzle which is a dischargeoutlet. Although not shown, the internal structure of the head 1412 issimilar to that of the head 1405. When the nozzle sizes of the head 1405and the head 1412 are different from each other, different materials canbe discharged with different widths simultaneously. Each head candischarge and draw a plurality of light emitting materials. In the caseof drawing over a large area, the same material can be simultaneouslydischarged to be drawn from a plurality of nozzles in order to improvethroughput. When a large substrate is used, the heads 1405 and 1412 canfreely move over the substrate in directions indicated by the solidarrows in FIG. 11, and a drawing region can be freely set. Thus, aplurality of the same patterns can be drawn over one substrate.

The step of discharging the composition may be performed under reducedpressure. Further, the substrate may be heated when the composition isdischarged. After the composition is discharged, either or both steps ofdrying and baking are performed. Both the drying and baking steps areheat treatments, but they have different purposes, temperatures, andtime periods. For example, drying is performed at 80 to 100° C. forthree minutes and a baking is performed at 200 to 550° C. for 15 to 60minutes. The steps of drying and baking are performed under normalatmospheric pressure or under reduced pressure by laser lightirradiation, rapid thermal annealing, heating using a heating furnace,or the like. Note that there is no particular limitation on when and howmany times the heat treatment is performed. The temperature forperforming the steps of drying and baking in a favorable manner dependson the material of the substrate and properties of the composition.

This embodiment mode can be combined with any other embodiment mode asappropriate.

Embodiment Mode 6

In this embodiment mode, electronic devices of the present invention,which includes the light emitting device described in Embodiment Mode 4,are described. The electronic devices of the present invention have adisplay portion manufactured using the organometallic complex describedin Embodiment Mode 1. In addition, the electronic devices of the presentinvention have the display portion which consumes lower power.

Examples of the electronic device having the light emitting elementmanufactured using an organometallic complex of the present inventionare cameras such as video cameras or digital cameras, goggle typedisplays, navigation systems, audio reproducing devices (e.g., car audiocomponents and audio components), computers, game machines, portableinformation terminals (e.g., mobile computers, cellular phones, portablegame machines, and e-book readers), and image reproducing devicesprovided with recording media (specifically, devices that are capable ofreproducing recording media such as digital versatile discs (DVDs) andprovided with a display device that can display the image). Specificexamples of these electronic devices are shown in FIGS. 6A to 6D.

FIG. 6A shows a television device according to the present invention,which includes a chassis 9101, a supporting base 9102, a display portion9103, a speaker portion 9104, a video input terminal 9105, and the like.In this television device, the display portion 9103 includes lightemitting elements arranged in matrix which are similar to light emittingelements described in Embodiment Modes 2 and 3. The light emittingelements have high emission efficiency. The display portion 9103 whichincludes the light emitting elements has similar characteristics.Accordingly, the television device consumes low power. Suchcharacteristics can dramatically reduce or downsize power supplycircuits in the television device, whereby the chassis 9101 and thesupporting base 9102 can be reduced in size and weight. In thetelevision device according to the present invention, low powerconsumption, high image quality, and reduced size and weight areachieved; therefore, a product suitable for living environment can beprovided.

FIG. 6B shows a computer according to the present invention, whichincludes a main body 9201, a chassis 9202, a display portion 9203, akeyboard 9204, an external connection port 9205, a pointing device 9206,and the like. In this computer, the display portion 9203 includes lightemitting elements arranged in matrix which are similar to light emittingelements described in Embodiment Modes 2 and 3. The light emittingelements have high emission efficiency. The display portion 9203 whichincludes the light emitting elements has similar characteristics.Accordingly, the computer consumes low power. Such characteristics candramatically reduce or downsize power supply circuits in the computer,whereby the main body 9201 and the chassis 9202 can be reduced in sizeand weight. In the computer according to the present invention, lowpower consumption, high image quality, and reduced size and weight areachieved; therefore, a product suitable for the environment can beprovided.

FIG. 6C shows a cellular phone according to the present invention, whichincludes a main body 9401, a chassis 9402, a display portion 9403, anaudio input portion 9404, an audio output portion 9405, an operation key9406, an external connection port 9407, an antenna 9408, and the like.In this cellular phone, the display portion 9403 includes light emittingelements arranged in matrix which are similar to light emitting elementsdescribed in Embodiment Modes 2 and 3. The light emitting elements havehigh emission efficiency. The display portion 9403 which includes thelight emitting elements has similar characteristics. Accordingly, thecellular phone consumes low power. Such characteristics can dramaticallyreduce or downsize power supply circuits in the cellular phone, wherebythe main body 9401 and the chassis 9402 can be reduced in size andweight. In the cellular phone according to the present invention, lowpower consumption, high image quality, and a small size and light weightare achieved; therefore, a product suitable for carrying can beprovided.

FIG. 6D shows a camera according to the present invention, whichincludes a main body 9501, a display portion 9502, a chassis 9503, anexternal connection port 9504, a remote control receiving portion 9505,an image receiving portion 9506, a battery 9507, an audio input portion9508, an operation key 9509, an eye piece portion 9510, and the like. Inthis camera, the display portion 9502 includes light emitting elementsarranged in matrix which are similar to light emitting elementsdescribed in Embodiment Modes 2 and 3. The light emitting elements arecharacterized by high emission efficiency. The display portion 9502which includes the light emitting elements has similar characteristics.Accordingly, the camera consumes low power. Such characteristics candramatically reduce or downsize power supply circuits in the camera,whereby the main body 9501 can be reduced in size and weight. In thecamera according to the present invention, low power consumption, highimage quality, and reduced size and weight are achieved; therefore, aproduct suitable for carrying can be provided.

As described above, the applicable range of the light emitting device ofthe present invention is so wide that the light emitting device can beapplied to electronic devices in various fields. By using the lightemitting element of the present invention, an electronic deviceincluding a display portion with low power consumption can be provided.Furthermore, the electronic device of the present invention includingthe light emitting element is manufactured using the compositiondescribed in Embodiment Mode 1, and therefore, is excellent in massproductivity. Also, the manufacturing cost is reduced because of highuse efficiency of the material, whereby a low cost electronic device canbe obtained.

The light emitting device of the present invention can also be used as alighting device. One mode in which the light emitting device of thepresent invention is used as a lighting device is described withreference to FIG. 7.

FIG. 7 shows an example of a liquid crystal display device in which thelight emitting device of the present invention is used as a backlight.The liquid crystal display device shown in FIG. 7 includes a chassis901, a liquid crystal layer 902, a backlight 903, and a chassis 904. Theliquid crystal layer 902 is connected to a driver IC 905. The lightemitting device of the present invention is used as the backlight 903,and current is supplied through a terminal 906.

When the light emitting device of the present invention is used as thebacklight of the liquid crystal display device, the backlight withreduced power consumption can be obtained. The light emitting device ofthe present invention is a lighting device with a plane emission area,and this emission area can be readily increased; accordingly, it ispossible that the backlight have a larger emission area and the liquidcrystal display device have a larger display area. Further, the lightemitting device of the present invention has a thin shape and consumeslow power; thus, the display device can also be reduced in thickness andpower consumption. In addition, the light emitting device of the presentinvention is formed using the composition described in Embodiment Mode1, and therefore, is excellent in mass productivity. Also, themanufacturing cost is reduced because of high use efficiency of thematerial, whereby a low cost light emitting device can be obtained.Accordingly, the liquid crystal display device to which the lightemitting device of the present invention is applied has similarcharacteristics.

FIG. 8 shows an example in which the light emitting device of thepresent invention is used as a table lamp which is a lighting device.The table lamp shown in FIG. 8 has a chassis 2001 and a light source2002, and the light emitting device of the present invention is used asthe light source 2002. The light emitting device of the presentinvention can emit light with high luminance, and thus it can illuminatehands doing delicate handwork or the like. The light emitting device ofthe present invention is manufactured using the composition described inEmbodiment Mode 1, and therefore, is excellent in mass productivity.Also, the manufacturing cost is reduced because of high use efficiencyof the material, whereby a low cost light emitting device can beobtained.

FIG. 9 shows an example in which a light emitting device of the presentinvention is used as an indoor lighting device 3001. Since the lightemitting device of the present invention can have a larger emissionarea, the light emitting device of the present invention can be used asa lighting device having a larger emission area. Further, the lightemitting device of the present invention has a thin shape and consumeslow power; accordingly, the light emitting device of the presentinvention can be used as a lighting device having a thin shape andconsuming low power. When a television device according to the presentinvention as described with reference to FIG. 6A is placed in a room inwhich a light emitting device according to the present invention is usedas the indoor lighting device 3001, public broadcasting and movies canbe watched. In such a case, since both of the devices consume low power,powerful images can be watched in a bright room without concern aboutelectricity charges.

Example 1 Synthesis Example 1

Synthesis Example 1 describes a specific example of synthesis ofbis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbr.:[Ir(tppr)₂(dpm)]), which is an organometallic complex of the presentinvention and is represented by a structural formula (147) described inEmbodiment Mode 1.

Step 1: Synthesis of 2,3,5-triphenylpyrazine (abbr.: Htppr)

First, 5.5 mL of a dibutyl ether solution of phenyl lithium(manufactured by Wako Pure Chemical Industries, Ltd., 2.1 mol/L) and 50mL of diethyl ether were mixed under a nitrogen atmosphere. Then, 2.43 gof 2,3-diphenylpyrazine was dropped into this solution while thesolution was being cooled, with ice, and the mixture was stirred at roomtemperature for 24 hours. Water was added to the mixture, and theorganic layer was extracted with diethyl ether. The extracted organiclayer was washed with water and dried with magnesium sulfate. After thedrying, an excess amount of activated manganese dioxide was added to theorganic layer, and the mixture was filtered. After the solvent of thesolution was distilled off, the obtained residue was recrystallized withethanol to give a pyrazine derivative, Htppr (a yellow powder, 56%yield). The synthetic scheme of Step 1 is represented by (a-1) below.

Step 2: Synthesis ofdi-μ-chloro-bis[bis(2,3,5-triphenylpyrazinato)iridium(III)] (abbr.:[Ir(tppr)₂Cl]₂)

Next, 1.08 g of Htppr, which is the pyrazine derivative obtained inabove-described Step 1, and 0.73 g of iridium chloride hydrate(IrCl₃.H₂O) (manufactured by Sigma-Aldrich Corp.) were mixed in a mixedsolvent of 30 mL of 2-ethoxyethanol and 10 mL of water. The mixture wasrefluxed for 16 hours under a nitrogen atmosphere. The precipitatedpowder was filtered and washed with ethanol, diethyl ether, and then,hexane to give a binuclear complex [Ir(tppr)₂Cl]₂ (an orange powder, 97%yield). The synthetic scheme of Step 2 is represented by (b-1) below.

Step 3: Synthesis ofbis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbr.:[Ir(tppr)₂(dpm)]

First, 25 mL of 2-ethoxyethanol, 0.40 g of [Ir(tppr)₂Cl]₂, which is abinuclear complex obtained in above-described Step 2, 0.14 mL ofdipivaloylmethane, and 0.25 g of sodium carbonate were put in aneggplant flask with a reflux pipe, and the air in the flack was replacedwith argon. Then, irradiation with microwave (2.45 GHz, 150 W) for 15minutes was performed to cause a reaction. The reacted solution wasfiltered and the obtained filtrate was recrystallized with ethanol. Theobtained red powder was washed with ethanol, and then, diethyl ether togive [Ir(tppr)₂(dpm)], which is an organometallic complex of the presentinvention (75% yield). For the irradiation of microwave, a microwavesynthesis system (Discover, manufactured by CEM Corporation) was used.The synthetic scheme of Step 3 is represented by (c-1) below.

An analysis result of the red powder obtained in Step 3 by nuclearmagnetic resonance spectrometry (¹H-NMR) is shown below and the ¹H NMRspectrum is shown in FIG. 12. The analysis result reveals that[Ir(tppr)₂(dpm)], which is an organometallic complex of the presentinvention which is represented by the structural formula (147), wasobtained in this Synthesis Example 1.

The ¹H NMR data is shown below. ¹H NMR. δ (CDCl₃): 1.02 (s, 18H), 5.64(s, 1H), 6.51 (m, 4H), 6.64 (m, 2H), 6.92 (d, 2H), 7.44-7.56 (m, 12H),7.80 (brs, 4H), 8.06 (d, 4H), 8.86 (s, 2H).

The decomposition temperature of the obtained organometallic complex ofthe present invention, [Ir(tppr)₂(dpm)], was measured with a high vacuumdifferential type differential thermal balance (TG-DTA2410SA,manufactured by Bruker AXS K.K.). The temperature increase rate was 10°C./min, and the temperature was increased under normal atmosphericpressure. Reduction in weight by 5% was observed at 327° C., which isindicative of favorable heat resistance of [Ir(tppr)₂(dpm)].

The absorption spectrum of [Ir(tppr)₂(dpm)] was measured with anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation), using a dichloromethane solution (0.094 mmol/L) at roomtemperature. Further, the emission spectrum of [Ir(tppr)₂(dpm)] wasmeasured with a fluorescence spectrophotometer (FS920, manufactured byHamamatsu Photonics K.K.), using a degassed dichloromethane solution(0.33 mmol/L) at room temperature. The excitation wavelength was 465 nm.The measurement result is shown in FIG. 13 in which the horizontal axesindicate a wavelength and the vertical axis indicates a molar absorptioncoefficient and an emission intensity.

As is shown in FIG. 13, an organometallic complex of the presentinvention [Ir(tppr)₂(dpm)] has a light emission peak at 630 nm and redlight was observed from the solution.

Example 2

In this Example, the solubility of an organometallic complex including apyrazine skeleton described in Embodiment Mode 1 was measured. Themeasurement was performed by examining the solubility in varioussolvents: 2-ethoxyethanol, isopropanol, and ethanol, which are alcohols;dioxane, which is ether; chloroform and dimethylformamide (DMF), whichare an organic solvent not including an aromatic ring; and toluene,which is an aromatic hydrocarbon-based solvent.

Among the complexes disclosed in Embodiment Mode 1, [Ir(tppr)₂(dpm)]represented by the structural formula (147), which was synthesized inExample 1, is selected as a measurement object. The solubility wasinvestigated.

The solubility test results of the sample are shown in Table 1 below. InTable 1, a cross indicates that the solubility x (g/L) is x<0.6, atriangle indicates that 0.9>x≧0.6, a circle indicates that 1.2>x≧0.9,and a double circle indicates that x≧1.2.

TABLE 1 sovents Solvents not having Structural Alcohols having aromaticformula Compound 2-ethoxy Ethers aromatic ring ring No. abbreviationethanol isopropanol ethanol dioxane chloroform DMF toluene (147)Ir(tppr)₂(dpm) ⊚ Δ Δ ⊚ ⊚ ⊚ Δ solubility x (g/L) x ≧ 1.2 . . . ⊚ 1.2 > x≧ 0.9 . . . ◯ 0.9 > x ≧ 0.6 . . . Δ x < 0.6 . . . X

[Ir(tppr)₂(dpm)] represented by the structural formula (147), which issynthesized in Example 1 has high solubility [Ir(tppr)₂(dpm)] showssufficiently high solubility (equal to or greater than 0.6 g/L) in2-ethoxyethanol, isopropanol, and ethanol, which are alcohols. It isfound that [Ir(tppr)₂(dpm)] has extremely high solubility (equal to orgreater than 1.2 g/L) in 2-ethoxyethanol in particular. Accordingly,[Ir(tppr)₂(dpm)] is preferably used for a composition for coating whichis used for a light emitting element manufactured by a wet process.

In addition, it is found that [Ir(tppr)₂(dpm)] represented by thestructural formula (147) also has extremely high solubility (equal to orgreater than 1.2 g/L) in dioxane, which is ether. In addition, it isfound that [Ir(tppr)₂(dpm)] also has extremely high solubility (equal toor greater than 1.2 g/L) in chloroform and dimethylformamide (DMF),which are an organic solvent not including an aromatic ring. Inaddition, [Ir(tppr)₂(dpm)] also has sufficiently high solubility (equalto or greater than 0.6 g/L) in toluene, which is an aromatichydrocarbon-based solvent. Accordingly, since [Ir(tppr)₂(dpm)]represented by the structural formula (147) has solubility in many kindsof solvents, [Ir(tppr)₂(dpm)] is preferably used for a composition forcoating.

As described above, the inventors of the present invention have foundthat solubility alcohols) is very distinctive.

Example 3

In this Example, a light emitting element using an organometalliccomplex of the present invention is described.

<<Preparation of Solution A>>

First, solution A including an organometallic complex of the presentinvention was prepared by dissolving 0.305 g ofbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(manufactured by Chemipro Kasei Kaisha, Ltd., a product purified bysublimation) (abbr.: BAlq), 0.0151 g ofN,N′-bis(3-methylphenyl)-N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine(manufactured by Tokyo Chemical Industry Co., Ltd.) (abbr.: TPD), and0.029 g of Ir(tppr)₂(dpm), which was synthesized in Example 1, in 20 mLof 2-methoxyethanol (manufactured by Kanto Chemical Co., Inc.). Notethat the solution A was bubbled with argon for one hour in order toremove oxygen, immediately before spin coating. In addition, thesolution A in a sample bottle was kept warm in an oven set at atemperature of 75° C. (atmospheric pressure) until it was used for filmformation. Structural formulae of BAlq, TPD, and Ir(tppr)₂(dpm) areshown below.

<<Preparation of Solution B>>

Solution B was prepared by dissolving 0.10 g of polyvinylcarbazole(Mw=1100000, manufactured by Sigma-Aldrich Corp.) (abbr.: PVK) and0.0255 g of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (manufacturedby Chemipro Kasei Kaisha, Ltd., a product purified by sublimation)(abbr.: NPB) in 40 mL of 1,4-dioxane (dehydration) (manufactured byKanto Chemical Co. Inc.). Structural formulae of PVK and NPB are shownbelow.

<Fabrication of Light Emitting Element 1>

First, a glass substrate over which a film of indium tin silicon oxide(ITSO) was formed with a thickness of 110 nm was prepared. The surfaceof the ITSO was covered with a polyimide film in a manner such that anarea of 2 mm×2 mm of the surface was exposed. Note that the ITSO servesas an anode of the light emitting element. As a pretreatment for formingthe light emitting element over this substrate, a mixed solution ofwater and 2-ethoxyethanol that were mixed in a volume ratio of 3:2 wasdropped onto the ITSO, and the ITSO was spin-coated with the mixedsolution.

Next, 15 mL of PEDOT/PSS (AI4083sp.gr, manufactured by H. C. StarckGmbH) and 10 mL of 2-ethoxyethanol were mixed to obtain a mixedsolution, and this mixed solution was dropped onto the ITSO. Immediatelythereafter, the ITSO was spin-coated with the mixed solution at aspinning rate of 2000 rpm for 60 seconds, and then, at a spinning rateof 3000 rpm for 10 seconds. Then, after an end portion of the substratewas wiped so as to expose a terminal connected to the ITSO, baking wasperformed at 110° C. for two hours in a vacuum dryer in which thepressure was reduced with a rotary pump, whereby a film of PEDOT/PSS wasformed with a thickness of 50 nm as a hole-injecting layer over theITSO.

Next, in a glove box (at an oxygen concentration of equal to or lowerthan 20 ppm and a moisture concentration of equal to or lower than 5ppm), the PEDOT/PSS was spin-coated with the solution B which hadalready been prepared. The spin coating was carried out at a spinningrate of 300 rpm for 2 seconds, and then, at a spinning rate of 2000 rpmfor 60 seconds, and further, at a spinning rate of 2500 rpm for 10seconds. Then, after an end portion of the substrate was wiped so as toexpose the terminal connected to the ITSO, vacuum heat drying wasperformed at 120° C. for one hour in a vacuum dryer in which thepressure is reduced with a rotary pump; thus, a hole-transporting layerwas formed. Note that when a film of the solution B was formed over aglass substrate under the above-described film formation conditions, thefilm thickness was found to be 15 nm by a measurement using a surfaceprofiler (Dektak V200Si, manufactured by Ulvac, Inc.).

Next, the substrate over which films of PEDOT/PSS and PVK/NPB wereformed was positioned in a glove box (at an oxygen concentration ofequal to or lower than 10 ppm and a moisture concentration of equal toor lower than 2 ppm) without the substrate being exposed to atmosphere;and then, the hole-transporting layer was spin-coated with solution A.The spin coating was carried out at a spinning rate of 300 rpm for 2seconds, and then, at a spinning rate of 500 rpm for 60 seconds, andfurther, at a spinning rate of 2500 rpm for 10 seconds. Then, after anend portion of the substrate was wiped so as to expose the terminalconnected to the ITSO, vacuum heat drying was performed at 100° C. forone hour in a vacuum dryer in which the pressure is reduced with arotary pump, whereby a light emitting layer was formed. Note that when afilm of solution A was formed over a glass substrate under theabove-described film formation conditions, the film thickness was foundto be 40 nm by a measurement using a surface profiler (Dektak V200Si,manufactured by Ulvac, Inc.).

Then, the above-described substrate was positioned in a vacuum vapordeposition apparatus without the substrate being exposed to atmosphere,and fixed to a holder in the vacuum vapor deposition apparatus so that asurface over which the light emitting layer was formed faced downward.

After the pressure in the vacuum vapor deposition apparatus was reducedto 10⁻⁴ Pa,bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbr.:BAlq) was vapor-deposited to have a thickness of 10 nm, whereby a firstelectron-transporting layer was formed. Bathophenanthroline (abbr.:BPhen) was vapor-deposited to have a thickness of 20 nm on the firstelectron-transporting layer, whereby a second electron-transportinglayer was formed. In addition, lithium fluoride (LiF) wasvapor-deposited to have a thickness of 1 nm on the secondelectron-transporting layer, whereby an electron-injecting layer wasformed. Lastly, a film of aluminum was formed to have a thickness of 200nm as a cathode. Thus, the light emitting element 1 of the presentinvention was obtained. Note that in the above-described vapordeposition process, vapor deposition was all performed by a resistanceheating method. A structural formula of BPhen is shown below.

<Operating Characteristics of Light Emitting Element 1>

Thus obtained light emitting element 1 was sealed in a glove box with anitrogen atmosphere so that the light emitting element 1 was not exposedto atmosphere. Then, the operating characteristics of the light emittingelement 1 were measured. Note that the measurements were carried out atroom temperature (an atmosphere kept at 25° C.).

FIG. 14 shows the emission spectrum of the light emitting element 1 whena current of 1 mA flows through the light emitting element 1.

When the luminance of the light emitting element 1 was 1025 cd/m², theCIE color coordinates were x=0.66 and y=0.34, the emission color wasred, and the current efficiency was 3.2 cd/A. In addition, when theluminance of the light emitting element 1 was 1025 cd/m², the voltagewas 12.0 V, the current density was 31.9 mA/cm², and the powerefficiency was 0.8 μm/W. The wavelength corresponding to the peak of thelight emission was 618 nm as shown in FIG. 14.

Accordingly, a light emitting element with high emission efficiency canbe obtained according to the present invention.

In addition, it is found that a layer can be further formed by a wetprocess over a layer including an organic compound by using acomposition of the present invention. In particular, as described inthis example, stacking layers by a wet process is possible by forming alayer which is insoluble in alcohol (the hole-transporting layer in thisexample) by a wet process, and then, applying a composition of thepresent invention using alcohol over the layer. Therefore, a method formanufacturing a light emitting element including a composition of thepresent invention is excellent in mass productivity and suitable forindustrial application. Furthermore, the material use efficiency ishigh; therefore, the manufacturing cost can be reduced.

Example 4 Synthesis Example 2

Synthesis Example 2 describes a specific example of synthesis ofbis(2,3,5-triphenylpyrazinato)(pivaloyltrifluoroacetonato)iridium(III)(abbr.: [Ir(tppr)₂(pFac)]), which is an organometallic complex of thepresent invention and is represented by a structural formula (148)described in Embodiment Mode 1.

Synthesis ofbis(2,3,5-triphenylpyrazinato)(pivaloyltrifluoroacetonato)iridium(III)(abbr.: [Ir(tppr)₂(pFac)]

First, 25 mL of 2-ethoxyethanol, 0.45 g of [Ir(tppr)₂Cl]₂, which is thebinuclear complex obtained in above-described Step 2 in SynthesisExample 1, 0.14 mL of pivaloyltrifluoroacetone, and 0.29 g of sodiumcarbonate were put in an eggplant flask with a reflux pipe, and the airin the flack was replaced with argon. Then, irradiation with microwave(2.45 GHz, 100 W) for 20 minutes was performed to cause a reaction.Dichloromethane was added to the reacted solution and was filtered. Theobtained filtrate was concentrated to precipitate orange powder. Thepowder was filtered and washed with ethanol, and then, ether to give[Ir(tppr)₂(pFac)], which is an organometallic complex of the presentinvention (76% yield). The synthetic scheme of this step is representedby (c-2) below.

An analysis result of the orange powder obtained in the above-describedstep by nuclear magnetic resonance spectrometry (¹H-NMR) is shown belowand the ¹H NMR spectrum is shown in FIG. 15. The analysis result revealsthat [Ir(tppr)₂(pFac)], which is an organometallic complex of thepresent invention which is represented by the foregoing structuralformula (148), was obtained in this Synthesis Example 2.

¹H-NMR. δ (CDCl₃): 1.06 (s, 9H), 5.88 (s, 1H), 6.45 (d, 2H), 6.54 (dt,2H), 6.67 (m, 2H), 6.92 (d, 2H), 7.48-7.57 (m, 12H), 7.82 (m, 4H), 8.08(ddd, 4H), 8.75 (s, 1H), 8.92 (s, 1H).

The absorption spectrum of [Ir(tppr)₂(pFac)] was measured with anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation), using a dichloromethane solution (0.090 mmol/L) at roomtemperature. Further, the emission spectrum of [Ir(tppr)₂(pFac)] wasmeasured with a fluorescence spectrophotometer (FS920, manufactured byHamamatsu Photonics K.K.), using a degassed dichloromethane solution(0.31 mmol/L) at room temperature. The measurement result is shown inFIG. 16 in which the horizontal axis indicates a wavelength and thevertical axes indicate a molar absorption coefficient and an emissionintensity.

As is shown in FIG. 16, an organometallic complex of the presentinvention [Ir(tppr)₂(pFac)] has a light emission peak at 610 nm andorange light was observed from the solution.

Example 5

In this Example, the solubility of an organometallic complex including apyrazine skeleton described in Embodiment Mode 1 was measured. Themeasurement was performed by examining the solubility in varioussolvents: dioxane, which is ether; chloroform and dimethylformamide(DMF), which are an organic solvent not including an aromatic ring; andtoluene, which is an aromatic hydrocarbon-based solvent.

Among the complexes disclosed in Embodiment Mode 1, [Ir(tppr)₂(pFac)]represented by the structural formula (148), which is synthesized inExample 4, was selected as a measurement object. The solubility wasinvestigated.

The solubility test results of the sample are shown in Table 2 below. InTable 2, a cross indicates that the solubility x (g/L) is x<0.6, atriangle indicates that 0.9>x≧0.6, a circle indicates that 1.2>x≧0.9,and a double circle indicates that x≧1.2.

TABLE 2 sovents having Structural Solvents not having aromatic formulaCompound Ethers aromatic ring ring No. abbreviation dioxane chloroformDMF toluene (148) Ir(tppr)₂(pFac) ⊚ ⊚ ⊚ ⊚ solubility x (g/L) x ≧ 1.2 . .. ⊚ 1.2 > x ≧ 0.9 . . . ◯ 0.9 > x ≧ 0.6 . . . Δ x < 0.6 . . . X

[Ir(tppr)₂(pFac)] represented by the structural formula (148), which issynthesized in Example 4 has high solubility, and therefore, ispreferably used for a composition for coating which is used for a lightemitting element manufactured a wet process.

In specific, it is found that [Ir(tppr)₂(pFac)] represented by thestructural formula (148) also has extremely high solubility (equal to orgreater than 1.2 g/L) in dioxane, which is ether. In addition, it isfound that [Ir(tppr)₂(pFac)] also has extremely high solubility (equalto or greater than 1.2 g/L) in chloroform and dimethylformamide (DMF),which are an organic solvent not including an aromatic ring. Inaddition, [Ir(tppr)₂(pFac)] also has extremely high solubility (equal toor greater than 1.2 g/L) in toluene, which is an aromatichydrocarbon-based solvent. Accordingly, since [Ir(tppr)₂(pFac)]represented by the structural formula (148) has solubility in many kindsof solvents, [Ir(tppr)₂(pFac)] is preferably used for a composition forcoating.

As described above, the inventors of the present invention have foundthat solubility becomes higher when a ligand represented by the generalformula (L1) is introduced.

This application is based on Japanese Patent Application serial no.2007-133341 filed with Japan Patent Office on May 18, 2007, the entirecontents of which are hereby incorporated by reference.

EXPLANATION OF REFERENCE

100: substrate, 101: first electrode, 102: second electrode, 103: ELlayer, 111 hole-injecting layer, 112: hole-transporting layer, 113:light emitting layer, 114 electron-transporting layer, 115:electron-injecting layer, 501: first electrode, 502 second electrode,511: first light emitting unit, 512: second light emitting unit, 513charge generation layer, 601: driver circuit portion (source side drivercircuit), 602 pixel portion, 603: driver circuit portion (gate sidedriver circuit), 604: sealing substrate 605: sealant, 607: space, 608:lead wiring, 609: flexible printed circuit (FPC), 610: elementsubstrate, 611: switching TFT, 612: current control TFT, 613: firstelectrode, 614: insulator, 616: EL layer, 617: second electrode, 618:light emitting element, 623: n-channel TFT, 624: p-channel TFT, 713:first electrode, 714: insulating layer, 716: layer includingorganometallic complex, 717: second electrode, 718: light emittingelement, 719: insulating layer, 730: droplet discharge device, 731:droplet, 732: layer containing composition, 901: chassis, 902: liquidcrystal layer, 903: backlight, 904: chassis, 905: driver IC, 906:terminal, 951: substrate, 952: electrode, 953: insulating layer, 954:partition layer, 955: EL layer, 956: electrode, 1400: substrate, 1403:droplet discharging means, 1404: imaging means, 1405: head, 1406: dottedline, 1407: control means, 1408: storage medium, 1409: image processingmeans, 1410: computer, 1411: marker, 1412: head, 1413: material supplysource, 1414: material supply source, 2001: chassis, 2002: light source,3001: lighting device, 9101: chassis, 9102: supporting base, 9103:display portion, 9104: speaker portion, 9105: video input terminal,9201: main body, 9202: chassis, 9203: display portion, 9204: keyboard,9205: external connection port, 9206: pointing device, 9401: main body,9402: chassis, 9403: display portion, 9404: audio input portion, 9405:audio output portion, 9406: operation key, 9407: external connectionport, 9408: antenna, 9501: main body, 9502: display portion, 9503:chassis, 9504: external connection port, 9505: remote control receivingportion, 9506: image receiving portion, 9507: battery, 9508: audio inputportion, 9509: operation key, 9510: eye piece portion.

The invention claimed is:
 1. An organometallic complex represented by ageneral formula (G1):

wherein: Ar represents an arylene group; R¹ represents an aryl group; R²represents an aryl group; R³ represents hydrogen; M is iridium; n is 2;and one of R²¹ and R²² represents an alkyl group having 2 to 10 carbonatoms or a haloalkyl group having 2 to 10 carbon atoms and the other onerepresents an alkyl group having 1 to 10 carbon atoms or a haloalkylgroup having 1 to 10 carbon atoms; and a solubility of theorganometallic complex in ethanol is equal to or higher than 0.6 g/L. 2.The organometallic complex according to claim 1, wherein one of R²¹ andR²² represents an alkyl group having 2 to 4 carbon atoms or a haloalkylgroup having 2 to 4 carbon atoms and the other one represents an alkylgroup having 1 to 4 carbon atoms or a haloalkyl group having 1 to 4carbon atoms.
 3. The organometallic complex according to claim 1,wherein each of R²¹ and R²² represents a branched alkyl group having 3to 4 carbon atoms.
 4. A composition including an organometallic complexaccording to claim 1 and a solvent.
 5. A light emitting elementcomprising: a pair of electrodes; and an organometallic complexaccording to claim 1 between the pair of electrodes.
 6. Anorganometallic complex represented by a general formula (G2):

wherein: R¹ represents, a phenyl group or a phenyl group having asubstituent; R² represents, a phenyl group or a phenyl group having asubstituent; R³ represents hydrogen; each of R⁴ to R⁷ represents any oneof hydrogen or an alkyl group; M is iridium; n is 2; one of R²¹ and R²²represents an alkyl group having 2 to 10 carbon atoms or a haloalkylgroup having 2 to 10 carbon atoms and the other one represents an alkylgroup having 1 to 10 carbon atoms or a haloalkyl group having 1 to 10carbon atoms; and wherein a solubility of the organometallic complex inethanol is equal to or higher than 0.6 g/L.
 7. The organometalliccomplex according to claim 6, wherein one of R²¹ and R²² represents analkyl group having 2 to 4 carbon atoms or a haloalkyl group having 2 to4 carbon atoms and the other one represents an alkyl group having 1 to 4carbon atoms or a haloalkyl group having 1 to 4 carbon atoms.
 8. Theorganometallic complex according to claim 6, wherein each of R²¹ and R²²represents a branched alkyl group having 3 to 4 carbon atoms.
 9. Anorganometallic complex represented by a general formula (G3):

wherein: R¹ represents a phenyl group or a phenyl group having asubstituent; R³ represents hydrogen; each of R⁴ to R¹² representshydrogen, an alkyl group, or a halogen group; M is iridium; n is 2; oneof R²¹ and R²² represents an alkyl group having 2 to 10 carbon atoms ora haloalkyl group having 2 to 10 carbon atoms and the other onerepresents an alkyl group having 1 to 10 carbon atoms or a haloalkylgroup having 1 to 10 carbon atoms; and wherein a solubility of theorganometallic complex in ethanol is equal to or higher than 0.6 g/L.10. The organometallic complex according to claim 9, wherein one of R²¹and R²² represents an alkyl group having 2 to 4 carbon atoms or ahaloalkyl group having 2 to 4 carbon atoms and the other one representsan alkyl group having 1 to 4 carbon atoms or a haloalkyl group having 1to 4 carbon atoms.
 11. The organometallic complex according to claim 9,wherein each of R²¹ and R²² represents a branched alkyl group having 3to 4 carbon atoms.